diff --git a/pkgs/racket-test-core/tests/racket/optimize.rktl b/pkgs/racket-test-core/tests/racket/optimize.rktl
index 47b50ee1d5..c27e1aa46b 100644
--- a/pkgs/racket-test-core/tests/racket/optimize.rktl
+++ b/pkgs/racket-test-core/tests/racket/optimize.rktl
@@ -904,6 +904,32 @@
 
     ))
 
+;; Check JIT handling of structure-reference sequencese
+(parameterize ([current-namespace (make-base-namespace)]
+               [eval-jit-enabled #t])
+  (eval '(module paper racket/base
+          (provide (all-defined-out))
+          (struct paper (width height folds) #:transparent)
+          (define (fold-letter l)
+            (for/fold ([l l]) ([i (in-range 100)])
+              (and (paper? l)
+                   (struct-copy paper l [folds i]))))
+          (define (refine-letter l)
+            (for/fold ([l l]) ([i (in-range 100)]) 
+              (and (paper? l)
+                   (struct-copy paper l [width i]))))))
+  (eval '(require 'paper))
+  (eval '(define letter (paper 8.5 11 0)))
+  (eval '(define formal-letter (chaperone-struct letter paper-height
+                                                 (lambda (s v)
+                                                   (unless (equal? v 11)
+                                                     (error "wrong"))
+                                                   v))))
+  (test #t eval '(equal? (fold-letter letter) (paper 8.5 11 99)))
+  (test #t eval '(equal? (fold-letter formal-letter) (paper 8.5 11 99)))
+  (test #t eval '(equal? (refine-letter letter) (paper 99 11 0)))
+  (test #t eval '(equal? (refine-letter formal-letter) (paper 99 11 0))))
+
 (define (comp=? c1 c2 want-same?)
   (let ([s1 (open-output-bytes)]
 	[s2 (open-output-bytes)])
diff --git a/racket/src/racket/src/gen-jit-ts.rkt b/racket/src/racket/src/gen-jit-ts.rkt
index 36bd02ef25..4de54e7a79 100644
--- a/racket/src/racket/src/gen-jit-ts.rkt
+++ b/racket/src/racket/src/gen-jit-ts.rkt
@@ -191,6 +191,7 @@
     s_v
     iSi_s
     siS_v
+    Sii_s
     z_p
     si_s
     sis_v
diff --git a/racket/src/racket/src/jit.h b/racket/src/racket/src/jit.h
index 0905a52760..6487e0ae72 100644
--- a/racket/src/racket/src/jit.h
+++ b/racket/src/racket/src/jit.h
@@ -319,7 +319,7 @@ struct scheme_jit_common_record {
   void *flvector_ref_check_index_code[JIT_NUM_FL_KINDS];
   void *flvector_set_check_index_code[JIT_NUM_FL_KINDS], *flvector_set_flonum_check_index_code[JIT_NUM_FL_KINDS];
   void *fxvector_ref_code, *fxvector_ref_check_index_code, *fxvector_set_code, *fxvector_set_check_index_code;
-  void *struct_raw_ref_code, *struct_raw_set_code;
+  void *struct_raw_ref_code, *struct_raw_set_code, *struct_raw_refs_code;
   void *syntax_e_code;
   void *on_demand_jit_arity_code, *in_progress_on_demand_jit_arity_code;
   void *get_stack_pointer_code;
diff --git a/racket/src/racket/src/jit_ts.c b/racket/src/racket/src/jit_ts.c
index 733d3cfac1..10faf239fb 100644
--- a/racket/src/racket/src/jit_ts.c
+++ b/racket/src/racket/src/jit_ts.c
@@ -96,6 +96,7 @@ define_ts_ss_s(scheme_byte_string_eq_2, FSRC_MARKS)
 define_ts_s_s(scheme_unbox, FSRC_MARKS)
 define_ts_si_s(scheme_struct_ref, FSRC_MARKS)
 define_ts_sis_v(scheme_struct_set, FSRC_MARKS)
+define_ts_Sii_s(unsafe_struct_refs, FSRC_MARKS)
 define_ts_iS_s(scheme_extract_checked_procedure, FSRC_MARKS)
 define_ts_iS_s(scheme_procedure_arity_includes, FSRC_MARKS)
 define_ts_ssi_s(vector_check_chaperone_of, FSRC_MARKS)
@@ -219,6 +220,7 @@ define_ts_s_s(scheme_box, FSRC_OTHER)
 # define ts_scheme_byte_string_length scheme_byte_string_length
 # define ts_scheme_struct_ref scheme_struct_ref
 # define ts_scheme_struct_set scheme_struct_set
+# define ts_unsafe_struct_refs unsafe_struct_refs
 # define ts_equal_as_bool equal_as_bool
 # define ts_scheme_string_eq_2 scheme_string_eq_2
 # define ts_scheme_byte_string_eq_2 scheme_byte_string_eq_2
diff --git a/racket/src/racket/src/jit_ts_def.c b/racket/src/racket/src/jit_ts_def.c
index 1ea6b65b66..ffe04270f1 100644
--- a/racket/src/racket/src/jit_ts_def.c
+++ b/racket/src/racket/src/jit_ts_def.c
@@ -187,59 +187,68 @@ static void ts_ ## id(Scheme_Object* g216, int g217, Scheme_Object** g218) \
   else \
      id(g216, g217, g218); \
 }
-#define define_ts_z_p(id, src_type) \
-static void* ts_ ## id(size_t g219) \
+#define define_ts_Sii_s(id, src_type) \
+static Scheme_Object* ts_ ## id(Scheme_Object** g219, int g220, int g221) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-    return scheme_rtcall_z_p("[" #id "]", src_type, id, g219); \
+    return scheme_rtcall_Sii_s("[" #id "]", src_type, id, g219, g220, g221); \
   else \
-    return id(g219); \
+    return id(g219, g220, g221); \
+}
+#define define_ts_z_p(id, src_type) \
+static void* ts_ ## id(size_t g222) \
+   XFORM_SKIP_PROC \
+{ \
+  if (scheme_use_rtcall) \
+    return scheme_rtcall_z_p("[" #id "]", src_type, id, g222); \
+  else \
+    return id(g222); \
 }
 #define define_ts_si_s(id, src_type) \
-static Scheme_Object* ts_ ## id(Scheme_Object* g220, int g221) \
+static Scheme_Object* ts_ ## id(Scheme_Object* g223, int g224) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-    return scheme_rtcall_si_s("[" #id "]", src_type, id, g220, g221); \
+    return scheme_rtcall_si_s("[" #id "]", src_type, id, g223, g224); \
   else \
-    return id(g220, g221); \
+    return id(g223, g224); \
 }
 #define define_ts_sis_v(id, src_type) \
-static void ts_ ## id(Scheme_Object* g222, int g223, Scheme_Object* g224) \
+static void ts_ ## id(Scheme_Object* g225, int g226, Scheme_Object* g227) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-     scheme_rtcall_sis_v("[" #id "]", src_type, id, g222, g223, g224); \
+     scheme_rtcall_sis_v("[" #id "]", src_type, id, g225, g226, g227); \
   else \
-     id(g222, g223, g224); \
+     id(g225, g226, g227); \
 }
 #define define_ts_ss_i(id, src_type) \
-static int ts_ ## id(Scheme_Object* g225, Scheme_Object* g226) \
+static int ts_ ## id(Scheme_Object* g228, Scheme_Object* g229) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-    return scheme_rtcall_ss_i("[" #id "]", src_type, id, g225, g226); \
+    return scheme_rtcall_ss_i("[" #id "]", src_type, id, g228, g229); \
   else \
-    return id(g225, g226); \
+    return id(g228, g229); \
 }
 #define define_ts_iSp_v(id, src_type) \
-static void ts_ ## id(int g227, Scheme_Object** g228, void* g229) \
+static void ts_ ## id(int g230, Scheme_Object** g231, void* g232) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-     scheme_rtcall_iSp_v("[" #id "]", src_type, id, g227, g228, g229); \
+     scheme_rtcall_iSp_v("[" #id "]", src_type, id, g230, g231, g232); \
   else \
-     id(g227, g228, g229); \
+     id(g230, g231, g232); \
 }
 #define define_ts_sss_s(id, src_type) \
-static Scheme_Object* ts_ ## id(Scheme_Object* g230, Scheme_Object* g231, Scheme_Object* g232) \
+static Scheme_Object* ts_ ## id(Scheme_Object* g233, Scheme_Object* g234, Scheme_Object* g235) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-    return scheme_rtcall_sss_s("[" #id "]", src_type, id, g230, g231, g232); \
+    return scheme_rtcall_sss_s("[" #id "]", src_type, id, g233, g234, g235); \
   else \
-    return id(g230, g231, g232); \
+    return id(g233, g234, g235); \
 }
 #define define_ts__v(id, src_type) \
 static void ts_ ## id() \
@@ -251,11 +260,11 @@ static void ts_ ## id() \
      id(); \
 }
 #define define_ts_iS_v(id, src_type) \
-static void ts_ ## id(int g233, Scheme_Object** g234) \
+static void ts_ ## id(int g236, Scheme_Object** g237) \
    XFORM_SKIP_PROC \
 { \
   if (scheme_use_rtcall) \
-     scheme_rtcall_iS_v("[" #id "]", src_type, id, g233, g234); \
+     scheme_rtcall_iS_v("[" #id "]", src_type, id, g236, g237); \
   else \
-     id(g233, g234); \
+     id(g236, g237); \
 }
diff --git a/racket/src/racket/src/jit_ts_future_glue.c b/racket/src/racket/src/jit_ts_future_glue.c
index 29998b59d7..f95e4778d1 100644
--- a/racket/src/racket/src/jit_ts_future_glue.c
+++ b/racket/src/racket/src/jit_ts_future_glue.c
@@ -1,4 +1,4 @@
- Scheme_Object* scheme_rtcall_siS_s(const char *who, int src_type, prim_siS_s f, Scheme_Object* g235, int g236, Scheme_Object** g237)
+ Scheme_Object* scheme_rtcall_siS_s(const char *who, int src_type, prim_siS_s f, Scheme_Object* g238, int g239, Scheme_Object** g240)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -13,9 +13,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g235;
-    future->arg_i1 = g236;
-    future->arg_S2 = g237;
+      future->arg_s0 = g238;
+    future->arg_i1 = g239;
+    future->arg_S2 = g240;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -25,7 +25,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_iSs_s(const char *who, int src_type, prim_iSs_s f, int g238, Scheme_Object** g239, Scheme_Object* g240)
+ Scheme_Object* scheme_rtcall_iSs_s(const char *who, int src_type, prim_iSs_s f, int g241, Scheme_Object** g242, Scheme_Object* g243)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -40,9 +40,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_i0 = g238;
-    future->arg_S1 = g239;
-    future->arg_s2 = g240;
+      future->arg_i0 = g241;
+    future->arg_S1 = g242;
+    future->arg_s2 = g243;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -52,7 +52,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_s_s(const char *who, int src_type, prim_s_s f, Scheme_Object* g241)
+ Scheme_Object* scheme_rtcall_s_s(const char *who, int src_type, prim_s_s f, Scheme_Object* g244)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -67,8 +67,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g241;
-  send_special_result(future, g241);
+      future->arg_s0 = g244;
+  send_special_result(future, g244);
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
   future = fts->thread->current_ft;
@@ -77,7 +77,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_n_s(const char *who, int src_type, prim_n_s f, Scheme_Native_Lambda* g242)
+ Scheme_Object* scheme_rtcall_n_s(const char *who, int src_type, prim_n_s f, Scheme_Native_Lambda* g245)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -92,7 +92,7 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_n0 = g242;
+      future->arg_n0 = g245;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -127,7 +127,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_ss_s(const char *who, int src_type, prim_ss_s f, Scheme_Object* g243, Scheme_Object* g244)
+ Scheme_Object* scheme_rtcall_ss_s(const char *who, int src_type, prim_ss_s f, Scheme_Object* g246, Scheme_Object* g247)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -142,8 +142,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g243;
-    future->arg_s1 = g244;
+      future->arg_s0 = g246;
+    future->arg_s1 = g247;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -153,7 +153,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_ssi_s(const char *who, int src_type, prim_ssi_s f, Scheme_Object* g245, Scheme_Object* g246, int g247)
+ Scheme_Object* scheme_rtcall_ssi_s(const char *who, int src_type, prim_ssi_s f, Scheme_Object* g248, Scheme_Object* g249, int g250)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -168,9 +168,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g245;
-    future->arg_s1 = g246;
-    future->arg_i2 = g247;
+      future->arg_s0 = g248;
+    future->arg_s1 = g249;
+    future->arg_i2 = g250;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -180,7 +180,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_tt_s(const char *who, int src_type, prim_tt_s f, const Scheme_Object* g248, const Scheme_Object* g249)
+ Scheme_Object* scheme_rtcall_tt_s(const char *who, int src_type, prim_tt_s f, const Scheme_Object* g251, const Scheme_Object* g252)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -195,8 +195,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_t0 = g248;
-    future->arg_t1 = g249;
+      future->arg_t0 = g251;
+    future->arg_t1 = g252;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -206,7 +206,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- MZ_MARK_STACK_TYPE scheme_rtcall_ss_m(const char *who, int src_type, prim_ss_m f, Scheme_Object* g250, Scheme_Object* g251)
+ MZ_MARK_STACK_TYPE scheme_rtcall_ss_m(const char *who, int src_type, prim_ss_m f, Scheme_Object* g253, Scheme_Object* g254)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -221,8 +221,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g250;
-    future->arg_s1 = g251;
+      future->arg_s0 = g253;
+    future->arg_s1 = g254;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -232,7 +232,7 @@
   
   return retval;
 }
- Scheme_Object* scheme_rtcall_Sl_s(const char *who, int src_type, prim_Sl_s f, Scheme_Object** g252, intptr_t g253)
+ Scheme_Object* scheme_rtcall_Sl_s(const char *who, int src_type, prim_Sl_s f, Scheme_Object** g255, intptr_t g256)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -247,8 +247,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_S0 = g252;
-    future->arg_l1 = g253;
+      future->arg_S0 = g255;
+    future->arg_l1 = g256;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -258,7 +258,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_l_s(const char *who, int src_type, prim_l_s f, intptr_t g254)
+ Scheme_Object* scheme_rtcall_l_s(const char *who, int src_type, prim_l_s f, intptr_t g257)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -273,7 +273,7 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_l0 = g254;
+      future->arg_l0 = g257;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -283,7 +283,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- void scheme_rtcall_bsi_v(const char *who, int src_type, prim_bsi_v f, Scheme_Bucket* g255, Scheme_Object* g256, int g257)
+ void scheme_rtcall_bsi_v(const char *who, int src_type, prim_bsi_v f, Scheme_Bucket* g258, Scheme_Object* g259, int g260)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -298,9 +298,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_b0 = g255;
-    future->arg_s1 = g256;
-    future->arg_i2 = g257;
+      future->arg_b0 = g258;
+    future->arg_s1 = g259;
+    future->arg_i2 = g260;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -310,7 +310,7 @@
   
   
 }
- void scheme_rtcall_iiS_v(const char *who, int src_type, prim_iiS_v f, int g258, int g259, Scheme_Object** g260)
+ void scheme_rtcall_iiS_v(const char *who, int src_type, prim_iiS_v f, int g261, int g262, Scheme_Object** g263)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -325,9 +325,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_i0 = g258;
-    future->arg_i1 = g259;
-    future->arg_S2 = g260;
+      future->arg_i0 = g261;
+    future->arg_i1 = g262;
+    future->arg_S2 = g263;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -337,7 +337,7 @@
   
   
 }
- void scheme_rtcall_ss_v(const char *who, int src_type, prim_ss_v f, Scheme_Object* g261, Scheme_Object* g262)
+ void scheme_rtcall_ss_v(const char *who, int src_type, prim_ss_v f, Scheme_Object* g264, Scheme_Object* g265)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -352,8 +352,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g261;
-    future->arg_s1 = g262;
+      future->arg_s0 = g264;
+    future->arg_s1 = g265;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -363,7 +363,7 @@
   
   
 }
- void scheme_rtcall_b_v(const char *who, int src_type, prim_b_v f, Scheme_Bucket* g263)
+ void scheme_rtcall_b_v(const char *who, int src_type, prim_b_v f, Scheme_Bucket* g266)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -378,7 +378,7 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_b0 = g263;
+      future->arg_b0 = g266;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -388,7 +388,7 @@
   
   
 }
- Scheme_Object* scheme_rtcall_sl_s(const char *who, int src_type, prim_sl_s f, Scheme_Object* g264, intptr_t g265)
+ Scheme_Object* scheme_rtcall_sl_s(const char *who, int src_type, prim_sl_s f, Scheme_Object* g267, intptr_t g268)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -403,8 +403,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g264;
-    future->arg_l1 = g265;
+      future->arg_s0 = g267;
+    future->arg_l1 = g268;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -414,7 +414,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_iS_s(const char *who, int src_type, prim_iS_s f, int g266, Scheme_Object** g267)
+ Scheme_Object* scheme_rtcall_iS_s(const char *who, int src_type, prim_iS_s f, int g269, Scheme_Object** g270)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -429,8 +429,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_i0 = g266;
-    future->arg_S1 = g267;
+      future->arg_i0 = g269;
+    future->arg_S1 = g270;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -440,7 +440,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- Scheme_Object* scheme_rtcall_S_s(const char *who, int src_type, prim_S_s f, Scheme_Object** g268)
+ Scheme_Object* scheme_rtcall_S_s(const char *who, int src_type, prim_S_s f, Scheme_Object** g271)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -455,7 +455,7 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_S0 = g268;
+      future->arg_S0 = g271;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -465,7 +465,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- void scheme_rtcall_s_v(const char *who, int src_type, prim_s_v f, Scheme_Object* g269)
+ void scheme_rtcall_s_v(const char *who, int src_type, prim_s_v f, Scheme_Object* g272)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -480,8 +480,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g269;
-  send_special_result(future, g269);
+      future->arg_s0 = g272;
+  send_special_result(future, g272);
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
   future = fts->thread->current_ft;
@@ -490,7 +490,7 @@
   
   
 }
- Scheme_Object* scheme_rtcall_iSi_s(const char *who, int src_type, prim_iSi_s f, int g270, Scheme_Object** g271, int g272)
+ Scheme_Object* scheme_rtcall_iSi_s(const char *who, int src_type, prim_iSi_s f, int g273, Scheme_Object** g274, int g275)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -505,9 +505,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_i0 = g270;
-    future->arg_S1 = g271;
-    future->arg_i2 = g272;
+      future->arg_i0 = g273;
+    future->arg_S1 = g274;
+    future->arg_i2 = g275;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -517,7 +517,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- void scheme_rtcall_siS_v(const char *who, int src_type, prim_siS_v f, Scheme_Object* g273, int g274, Scheme_Object** g275)
+ void scheme_rtcall_siS_v(const char *who, int src_type, prim_siS_v f, Scheme_Object* g276, int g277, Scheme_Object** g278)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -532,9 +532,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g273;
-    future->arg_i1 = g274;
-    future->arg_S2 = g275;
+      future->arg_s0 = g276;
+    future->arg_i1 = g277;
+    future->arg_S2 = g278;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -544,7 +544,34 @@
   
   
 }
- void* scheme_rtcall_z_p(const char *who, int src_type, prim_z_p f, size_t g276)
+ Scheme_Object* scheme_rtcall_Sii_s(const char *who, int src_type, prim_Sii_s f, Scheme_Object** g279, int g280, int g281)
+   XFORM_SKIP_PROC
+{
+  Scheme_Future_Thread_State *fts = scheme_future_thread_state;
+  future_t *future;
+  double tm;
+  Scheme_Object* retval;
+
+  future = fts->thread->current_ft;
+  future->prim_protocol = SIG_Sii_s;
+  future->prim_func = f;
+  tm = get_future_timestamp();
+  future->time_of_request = tm;
+  future->source_of_request = who;
+  future->source_type = src_type;
+      future->arg_S0 = g279;
+    future->arg_i1 = g280;
+    future->arg_i2 = g281;
+  
+  future_do_runtimecall(fts, (void*)f, 0, 1, 0);
+  fts->thread = scheme_current_thread;
+  future = fts->thread->current_ft;
+  retval = future->retval_s;
+  future->retval_s = 0;
+  receive_special_result(future, retval, 1);
+  return retval;
+}
+ void* scheme_rtcall_z_p(const char *who, int src_type, prim_z_p f, size_t g282)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -559,7 +586,7 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_z0 = g276;
+      future->arg_z0 = g282;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -569,7 +596,7 @@
   
   return retval;
 }
- Scheme_Object* scheme_rtcall_si_s(const char *who, int src_type, prim_si_s f, Scheme_Object* g277, int g278)
+ Scheme_Object* scheme_rtcall_si_s(const char *who, int src_type, prim_si_s f, Scheme_Object* g283, int g284)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -584,8 +611,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g277;
-    future->arg_i1 = g278;
+      future->arg_s0 = g283;
+    future->arg_i1 = g284;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -595,7 +622,7 @@
   receive_special_result(future, retval, 1);
   return retval;
 }
- void scheme_rtcall_sis_v(const char *who, int src_type, prim_sis_v f, Scheme_Object* g279, int g280, Scheme_Object* g281)
+ void scheme_rtcall_sis_v(const char *who, int src_type, prim_sis_v f, Scheme_Object* g285, int g286, Scheme_Object* g287)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -610,9 +637,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g279;
-    future->arg_i1 = g280;
-    future->arg_s2 = g281;
+      future->arg_s0 = g285;
+    future->arg_i1 = g286;
+    future->arg_s2 = g287;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -622,7 +649,7 @@
   
   
 }
- int scheme_rtcall_ss_i(const char *who, int src_type, prim_ss_i f, Scheme_Object* g282, Scheme_Object* g283)
+ int scheme_rtcall_ss_i(const char *who, int src_type, prim_ss_i f, Scheme_Object* g288, Scheme_Object* g289)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -637,8 +664,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g282;
-    future->arg_s1 = g283;
+      future->arg_s0 = g288;
+    future->arg_s1 = g289;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -648,7 +675,7 @@
   
   return retval;
 }
- void scheme_rtcall_iSp_v(const char *who, int src_type, prim_iSp_v f, int g284, Scheme_Object** g285, void* g286)
+ void scheme_rtcall_iSp_v(const char *who, int src_type, prim_iSp_v f, int g290, Scheme_Object** g291, void* g292)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -663,9 +690,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_i0 = g284;
-    future->arg_S1 = g285;
-    future->arg_p2 = g286;
+      future->arg_i0 = g290;
+    future->arg_S1 = g291;
+    future->arg_p2 = g292;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -675,7 +702,7 @@
   
   
 }
- Scheme_Object* scheme_rtcall_sss_s(const char *who, int src_type, prim_sss_s f, Scheme_Object* g287, Scheme_Object* g288, Scheme_Object* g289)
+ Scheme_Object* scheme_rtcall_sss_s(const char *who, int src_type, prim_sss_s f, Scheme_Object* g293, Scheme_Object* g294, Scheme_Object* g295)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -690,9 +717,9 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_s0 = g287;
-    future->arg_s1 = g288;
-    future->arg_s2 = g289;
+      future->arg_s0 = g293;
+    future->arg_s1 = g294;
+    future->arg_s2 = g295;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
@@ -727,7 +754,7 @@
   
   
 }
- void scheme_rtcall_iS_v(const char *who, int src_type, prim_iS_v f, int g290, Scheme_Object** g291)
+ void scheme_rtcall_iS_v(const char *who, int src_type, prim_iS_v f, int g296, Scheme_Object** g297)
    XFORM_SKIP_PROC
 {
   Scheme_Future_Thread_State *fts = scheme_future_thread_state;
@@ -742,8 +769,8 @@
   future->time_of_request = tm;
   future->source_of_request = who;
   future->source_type = src_type;
-      future->arg_i0 = g290;
-    future->arg_S1 = g291;
+      future->arg_i0 = g296;
+    future->arg_S1 = g297;
   
   future_do_runtimecall(fts, (void*)f, 0, 1, 0);
   fts->thread = scheme_current_thread;
diff --git a/racket/src/racket/src/jit_ts_protos.h b/racket/src/racket/src/jit_ts_protos.h
index 1078efb1f0..bb96f2c95e 100644
--- a/racket/src/racket/src/jit_ts_protos.h
+++ b/racket/src/racket/src/jit_ts_protos.h
@@ -1,87 +1,90 @@
 #define SIG_siS_s 11
 typedef Scheme_Object* (*prim_siS_s)(Scheme_Object*, int, Scheme_Object**);
-Scheme_Object* scheme_rtcall_siS_s(const char *who, int src_type, prim_siS_s f, Scheme_Object* g349, int g350, Scheme_Object** g351);
+Scheme_Object* scheme_rtcall_siS_s(const char *who, int src_type, prim_siS_s f, Scheme_Object* g358, int g359, Scheme_Object** g360);
 #define SIG_iSs_s 12
 typedef Scheme_Object* (*prim_iSs_s)(int, Scheme_Object**, Scheme_Object*);
-Scheme_Object* scheme_rtcall_iSs_s(const char *who, int src_type, prim_iSs_s f, int g352, Scheme_Object** g353, Scheme_Object* g354);
+Scheme_Object* scheme_rtcall_iSs_s(const char *who, int src_type, prim_iSs_s f, int g361, Scheme_Object** g362, Scheme_Object* g363);
 #define SIG_s_s 13
 typedef Scheme_Object* (*prim_s_s)(Scheme_Object*);
-Scheme_Object* scheme_rtcall_s_s(const char *who, int src_type, prim_s_s f, Scheme_Object* g355);
+Scheme_Object* scheme_rtcall_s_s(const char *who, int src_type, prim_s_s f, Scheme_Object* g364);
 #define SIG_n_s 14
 typedef Scheme_Object* (*prim_n_s)(Scheme_Native_Lambda*);
-Scheme_Object* scheme_rtcall_n_s(const char *who, int src_type, prim_n_s f, Scheme_Native_Lambda* g356);
+Scheme_Object* scheme_rtcall_n_s(const char *who, int src_type, prim_n_s f, Scheme_Native_Lambda* g365);
 #define SIG__s 15
 typedef Scheme_Object* (*prim__s)();
 Scheme_Object* scheme_rtcall__s(const char *who, int src_type, prim__s f );
 #define SIG_ss_s 16
 typedef Scheme_Object* (*prim_ss_s)(Scheme_Object*, Scheme_Object*);
-Scheme_Object* scheme_rtcall_ss_s(const char *who, int src_type, prim_ss_s f, Scheme_Object* g357, Scheme_Object* g358);
+Scheme_Object* scheme_rtcall_ss_s(const char *who, int src_type, prim_ss_s f, Scheme_Object* g366, Scheme_Object* g367);
 #define SIG_ssi_s 17
 typedef Scheme_Object* (*prim_ssi_s)(Scheme_Object*, Scheme_Object*, int);
-Scheme_Object* scheme_rtcall_ssi_s(const char *who, int src_type, prim_ssi_s f, Scheme_Object* g359, Scheme_Object* g360, int g361);
+Scheme_Object* scheme_rtcall_ssi_s(const char *who, int src_type, prim_ssi_s f, Scheme_Object* g368, Scheme_Object* g369, int g370);
 #define SIG_tt_s 18
 typedef Scheme_Object* (*prim_tt_s)(const Scheme_Object*, const Scheme_Object*);
-Scheme_Object* scheme_rtcall_tt_s(const char *who, int src_type, prim_tt_s f, const Scheme_Object* g362, const Scheme_Object* g363);
+Scheme_Object* scheme_rtcall_tt_s(const char *who, int src_type, prim_tt_s f, const Scheme_Object* g371, const Scheme_Object* g372);
 #define SIG_ss_m 19
 typedef MZ_MARK_STACK_TYPE (*prim_ss_m)(Scheme_Object*, Scheme_Object*);
-MZ_MARK_STACK_TYPE scheme_rtcall_ss_m(const char *who, int src_type, prim_ss_m f, Scheme_Object* g364, Scheme_Object* g365);
+MZ_MARK_STACK_TYPE scheme_rtcall_ss_m(const char *who, int src_type, prim_ss_m f, Scheme_Object* g373, Scheme_Object* g374);
 #define SIG_Sl_s 20
 typedef Scheme_Object* (*prim_Sl_s)(Scheme_Object**, intptr_t);
-Scheme_Object* scheme_rtcall_Sl_s(const char *who, int src_type, prim_Sl_s f, Scheme_Object** g366, intptr_t g367);
+Scheme_Object* scheme_rtcall_Sl_s(const char *who, int src_type, prim_Sl_s f, Scheme_Object** g375, intptr_t g376);
 #define SIG_l_s 21
 typedef Scheme_Object* (*prim_l_s)(intptr_t);
-Scheme_Object* scheme_rtcall_l_s(const char *who, int src_type, prim_l_s f, intptr_t g368);
+Scheme_Object* scheme_rtcall_l_s(const char *who, int src_type, prim_l_s f, intptr_t g377);
 #define SIG_bsi_v 22
 typedef void (*prim_bsi_v)(Scheme_Bucket*, Scheme_Object*, int);
-void scheme_rtcall_bsi_v(const char *who, int src_type, prim_bsi_v f, Scheme_Bucket* g369, Scheme_Object* g370, int g371);
+void scheme_rtcall_bsi_v(const char *who, int src_type, prim_bsi_v f, Scheme_Bucket* g378, Scheme_Object* g379, int g380);
 #define SIG_iiS_v 23
 typedef void (*prim_iiS_v)(int, int, Scheme_Object**);
-void scheme_rtcall_iiS_v(const char *who, int src_type, prim_iiS_v f, int g372, int g373, Scheme_Object** g374);
+void scheme_rtcall_iiS_v(const char *who, int src_type, prim_iiS_v f, int g381, int g382, Scheme_Object** g383);
 #define SIG_ss_v 24
 typedef void (*prim_ss_v)(Scheme_Object*, Scheme_Object*);
-void scheme_rtcall_ss_v(const char *who, int src_type, prim_ss_v f, Scheme_Object* g375, Scheme_Object* g376);
+void scheme_rtcall_ss_v(const char *who, int src_type, prim_ss_v f, Scheme_Object* g384, Scheme_Object* g385);
 #define SIG_b_v 25
 typedef void (*prim_b_v)(Scheme_Bucket*);
-void scheme_rtcall_b_v(const char *who, int src_type, prim_b_v f, Scheme_Bucket* g377);
+void scheme_rtcall_b_v(const char *who, int src_type, prim_b_v f, Scheme_Bucket* g386);
 #define SIG_sl_s 26
 typedef Scheme_Object* (*prim_sl_s)(Scheme_Object*, intptr_t);
-Scheme_Object* scheme_rtcall_sl_s(const char *who, int src_type, prim_sl_s f, Scheme_Object* g378, intptr_t g379);
+Scheme_Object* scheme_rtcall_sl_s(const char *who, int src_type, prim_sl_s f, Scheme_Object* g387, intptr_t g388);
 #define SIG_iS_s 27
 typedef Scheme_Object* (*prim_iS_s)(int, Scheme_Object**);
-Scheme_Object* scheme_rtcall_iS_s(const char *who, int src_type, prim_iS_s f, int g380, Scheme_Object** g381);
+Scheme_Object* scheme_rtcall_iS_s(const char *who, int src_type, prim_iS_s f, int g389, Scheme_Object** g390);
 #define SIG_S_s 28
 typedef Scheme_Object* (*prim_S_s)(Scheme_Object**);
-Scheme_Object* scheme_rtcall_S_s(const char *who, int src_type, prim_S_s f, Scheme_Object** g382);
+Scheme_Object* scheme_rtcall_S_s(const char *who, int src_type, prim_S_s f, Scheme_Object** g391);
 #define SIG_s_v 29
 typedef void (*prim_s_v)(Scheme_Object*);
-void scheme_rtcall_s_v(const char *who, int src_type, prim_s_v f, Scheme_Object* g383);
+void scheme_rtcall_s_v(const char *who, int src_type, prim_s_v f, Scheme_Object* g392);
 #define SIG_iSi_s 30
 typedef Scheme_Object* (*prim_iSi_s)(int, Scheme_Object**, int);
-Scheme_Object* scheme_rtcall_iSi_s(const char *who, int src_type, prim_iSi_s f, int g384, Scheme_Object** g385, int g386);
+Scheme_Object* scheme_rtcall_iSi_s(const char *who, int src_type, prim_iSi_s f, int g393, Scheme_Object** g394, int g395);
 #define SIG_siS_v 31
 typedef void (*prim_siS_v)(Scheme_Object*, int, Scheme_Object**);
-void scheme_rtcall_siS_v(const char *who, int src_type, prim_siS_v f, Scheme_Object* g387, int g388, Scheme_Object** g389);
-#define SIG_z_p 32
+void scheme_rtcall_siS_v(const char *who, int src_type, prim_siS_v f, Scheme_Object* g396, int g397, Scheme_Object** g398);
+#define SIG_Sii_s 32
+typedef Scheme_Object* (*prim_Sii_s)(Scheme_Object**, int, int);
+Scheme_Object* scheme_rtcall_Sii_s(const char *who, int src_type, prim_Sii_s f, Scheme_Object** g399, int g400, int g401);
+#define SIG_z_p 33
 typedef void* (*prim_z_p)(size_t);
-void* scheme_rtcall_z_p(const char *who, int src_type, prim_z_p f, size_t g390);
-#define SIG_si_s 33
+void* scheme_rtcall_z_p(const char *who, int src_type, prim_z_p f, size_t g402);
+#define SIG_si_s 34
 typedef Scheme_Object* (*prim_si_s)(Scheme_Object*, int);
-Scheme_Object* scheme_rtcall_si_s(const char *who, int src_type, prim_si_s f, Scheme_Object* g391, int g392);
-#define SIG_sis_v 34
+Scheme_Object* scheme_rtcall_si_s(const char *who, int src_type, prim_si_s f, Scheme_Object* g403, int g404);
+#define SIG_sis_v 35
 typedef void (*prim_sis_v)(Scheme_Object*, int, Scheme_Object*);
-void scheme_rtcall_sis_v(const char *who, int src_type, prim_sis_v f, Scheme_Object* g393, int g394, Scheme_Object* g395);
-#define SIG_ss_i 35
+void scheme_rtcall_sis_v(const char *who, int src_type, prim_sis_v f, Scheme_Object* g405, int g406, Scheme_Object* g407);
+#define SIG_ss_i 36
 typedef int (*prim_ss_i)(Scheme_Object*, Scheme_Object*);
-int scheme_rtcall_ss_i(const char *who, int src_type, prim_ss_i f, Scheme_Object* g396, Scheme_Object* g397);
-#define SIG_iSp_v 36
+int scheme_rtcall_ss_i(const char *who, int src_type, prim_ss_i f, Scheme_Object* g408, Scheme_Object* g409);
+#define SIG_iSp_v 37
 typedef void (*prim_iSp_v)(int, Scheme_Object**, void*);
-void scheme_rtcall_iSp_v(const char *who, int src_type, prim_iSp_v f, int g398, Scheme_Object** g399, void* g400);
-#define SIG_sss_s 37
+void scheme_rtcall_iSp_v(const char *who, int src_type, prim_iSp_v f, int g410, Scheme_Object** g411, void* g412);
+#define SIG_sss_s 38
 typedef Scheme_Object* (*prim_sss_s)(Scheme_Object*, Scheme_Object*, Scheme_Object*);
-Scheme_Object* scheme_rtcall_sss_s(const char *who, int src_type, prim_sss_s f, Scheme_Object* g401, Scheme_Object* g402, Scheme_Object* g403);
-#define SIG__v 38
+Scheme_Object* scheme_rtcall_sss_s(const char *who, int src_type, prim_sss_s f, Scheme_Object* g413, Scheme_Object* g414, Scheme_Object* g415);
+#define SIG__v 39
 typedef void (*prim__v)();
 void scheme_rtcall__v(const char *who, int src_type, prim__v f );
-#define SIG_iS_v 39
+#define SIG_iS_v 40
 typedef void (*prim_iS_v)(int, Scheme_Object**);
-void scheme_rtcall_iS_v(const char *who, int src_type, prim_iS_v f, int g404, Scheme_Object** g405);
+void scheme_rtcall_iS_v(const char *who, int src_type, prim_iS_v f, int g416, Scheme_Object** g417);
diff --git a/racket/src/racket/src/jit_ts_runtime_glue.c b/racket/src/racket/src/jit_ts_runtime_glue.c
index 3f826b8039..5b7ceff16d 100644
--- a/racket/src/racket/src/jit_ts_runtime_glue.c
+++ b/racket/src/racket/src/jit_ts_runtime_glue.c
@@ -290,6 +290,20 @@ case SIG_siS_v:
      f(arg_s0, arg_i1, arg_S2);
      
      
+     break;
+  }
+case SIG_Sii_s:
+  {
+     prim_Sii_s f = (prim_Sii_s)future->prim_func;
+     GC_CAN_IGNORE Scheme_Object* retval;
+     JIT_TS_LOCALIZE(Scheme_Object**, arg_S0); JIT_TS_LOCALIZE(int, arg_i1); JIT_TS_LOCALIZE(int, arg_i2);
+     
+     future->arg_S0 = NULL;
+     ADJUST_RS_ARG(future, arg_S0);
+     retval = 
+     f(arg_S0, arg_i1, arg_i2);
+     future->retval_s = retval;
+     send_special_result(future, retval);
      break;
   }
 case SIG_z_p:
diff --git a/racket/src/racket/src/jitcall.c b/racket/src/racket/src/jitcall.c
index 7d01aa6f63..c8b6413d26 100644
--- a/racket/src/racket/src/jitcall.c
+++ b/racket/src/racket/src/jitcall.c
@@ -36,6 +36,11 @@ static int generate_argument_boxing(mz_jit_state *jitter, Scheme_Lambda *lam,
                                     Scheme_App_Rec *app, Scheme_Object **alt_rands);
 #endif
 
+static int detect_unsafe_struct_refs(Scheme_Object *arg, Scheme_Object **alt_rands, Scheme_App_Rec *app,
+                                     int i, int num_rands, int shift);
+static int generate_unsafe_struct_ref_sequence(mz_jit_state *jitter, Scheme_Object *arg, Scheme_Object *last_arg,
+                                               int count, int stack_pos);
+
 int scheme_direct_call_count, scheme_indirect_call_count;
 
 struct jit_direct_arg {
@@ -1783,7 +1788,7 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
    If no_call is 2, then rator is not necssarily evaluated. 
    If no_call is 1, then rator is left in V1 and arguments are on runstack. */
 {
-  int i, offset, need_safety = 0, apply_to_list = 0;
+  int i, offset, need_safety = 0, apply_to_list = 0, num_unsafe_struct_refs;
   int direct_prim = 0, need_non_tail = 0, direct_native = 0, direct_self = 0, nontail_self = 0;
   Scheme_Native_Closure *inline_direct_native = NULL;
   int almost_inline_direct_native = 0;
@@ -2113,10 +2118,26 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
       need_safety = 0;
     }
 #ifdef USE_FLONUM_UNBOXING
-    if (direct_lam
-        && (SCHEME_LAMBDA_FLAGS(direct_lam) & LAMBDA_HAS_TYPED_ARGS)
-        && (CLOSURE_ARGUMENT_IS_FLONUM(direct_lam, i+args_already_in_place)
-            || CLOSURE_ARGUMENT_IS_EXTFLONUM(direct_lam, i+args_already_in_place))) {
+    if (direct_lam)
+      num_unsafe_struct_refs = 0;
+    else
+#endif
+      num_unsafe_struct_refs = detect_unsafe_struct_refs(arg, alt_rands, app, i, num_rands, 1+args_already_in_place);
+    if (num_unsafe_struct_refs > 1) {
+      /* Found a sequence of `(unsafed-struct-ref id 'number)` with
+         sequential `number`s, so extract the whole group at once */
+      v = (alt_rands 
+           ? alt_rands[i+1+args_already_in_place+num_unsafe_struct_refs-1]
+           : app->args[i+1+args_already_in_place+num_unsafe_struct_refs-1]);
+      mz_rs_sync();
+      generate_unsafe_struct_ref_sequence(jitter, arg, v, num_unsafe_struct_refs, i + offset);
+      CHECK_LIMIT();
+      i += (num_unsafe_struct_refs - 1);
+#ifdef USE_FLONUM_UNBOXING
+    } else if (direct_lam
+               && (SCHEME_LAMBDA_FLAGS(direct_lam) & LAMBDA_HAS_TYPED_ARGS)
+               && (CLOSURE_ARGUMENT_IS_FLONUM(direct_lam, i+args_already_in_place)
+                   || CLOSURE_ARGUMENT_IS_EXTFLONUM(direct_lam, i+args_already_in_place))) {
       int directly;
       int extfl;
       extfl = CLOSURE_ARGUMENT_IS_EXTFLONUM(direct_lam, i+args_already_in_place);
@@ -2149,13 +2170,12 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
       } else {
         (void)jit_movi_p(JIT_R0, NULL);
       }
-    } else
 #endif
-      if (inline_direct_args) {
-        if (inline_direct_args[i].gen)
+    } else if (inline_direct_args) {
+      if (inline_direct_args[i].gen)
           scheme_generate(arg, jitter, 0, 0, 0, inline_direct_args[i].reg, NULL, NULL);
-      } else
-        scheme_generate_non_tail(arg, jitter, 0, !need_non_tail, 0); /* sync'd below */
+    } else
+      scheme_generate_non_tail(arg, jitter, 0, !need_non_tail, 0); /* sync'd below */
     RESUME_JIT_DATA();
     CHECK_LIMIT();
 
@@ -2397,4 +2417,91 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
   return is_tail ? 2 : 1;
 }
 
+
+static int detect_unsafe_struct_refs(Scheme_Object *arg, Scheme_Object **alt_rands, Scheme_App_Rec *app,
+                                     int i, int num_rands, int shift)
+/* Look for `(unsafe-struct-ref id 'num)` ... as a sequence of
+   arguments, which shows up as a result of `struct-copy`, and return
+   the length of the sequence. Instead of performing each
+   `unsafe-struct-ref` separately, which involves a chaperone test
+   each time, we'll test once and extract all. */
+{
+  Scheme_App3_Rec *app3, *next_app3;
+  Scheme_Object *next_arg;
+
+  if (SAME_TYPE(SCHEME_TYPE(arg), scheme_application3_type)) {
+    app3 = (Scheme_App3_Rec *)arg;
+    if (SAME_OBJ(app3->rator, scheme_unsafe_struct_ref_proc)
+        && SAME_TYPE(SCHEME_TYPE(app3->rand1), scheme_local_type)
+        && SCHEME_INTP(app3->rand2)) {
+      int seq = 1, delta = SCHEME_INT_VAL(app3->rand2) - i;
+      i++;
+      while (i < num_rands) {
+        next_arg = (alt_rands ? alt_rands[i+shift] : app->args[i+shift]);
+        if (SAME_TYPE(SCHEME_TYPE(next_arg), scheme_application3_type)) {
+          next_app3 = (Scheme_App3_Rec *)next_arg;
+          if (SAME_OBJ(next_app3->rator, scheme_unsafe_struct_ref_proc)
+              && SAME_TYPE(SCHEME_TYPE(next_app3->rand1), scheme_local_type)
+              && SCHEME_INTP(next_app3->rand2)
+              && (SCHEME_INT_VAL(next_app3->rand2) == i + delta)
+              && (SCHEME_LOCAL_POS(next_app3->rand1) == SCHEME_LOCAL_POS(app3->rand1))) {
+            seq++;
+            i++;
+          } else
+            break;
+        } else
+          break;
+      }
+      return seq;
+    }
+  }
+  
+  return 0;
+}
+
+static int generate_unsafe_struct_ref_sequence(mz_jit_state *jitter, Scheme_Object *arg, Scheme_Object *last_arg,
+                                               int count, int stack_pos)
+/* Implement a sequence discovered by `detect_unsafe_struct_refs()`. */
+{
+  Scheme_App3_Rec *app3 = (Scheme_App3_Rec *)arg;
+  int i, base = SCHEME_INT_VAL(app3->rand2);
+  GC_CAN_IGNORE jit_insn *ref, *refslow, *ref2;
+
+  /* Using `last_arg` ensures that we clear the local, if needed */
+  mz_runstack_skipped(jitter, 2);
+  scheme_generate(((Scheme_App3_Rec *)last_arg)->rand1, jitter, 0, 0, 0, JIT_R0, NULL, NULL);
+  CHECK_LIMIT();
+  mz_runstack_unskipped(jitter, 2);
+
+  /* Check for chaperones, and take slow path if found */
+  __START_SHORT_JUMPS__(1);
+  jit_ldxi_s(JIT_R2, JIT_R0, &((Scheme_Object *)0x0)->type);
+  ref = jit_bnei_i(jit_forward(), JIT_R2, scheme_chaperone_type);
+  refslow = jit_get_ip();
+  jit_addi_p(JIT_R1, JIT_RUNSTACK, WORDS_TO_BYTES(stack_pos));
+  jit_str_p(JIT_R1, JIT_R0);
+  jit_movi_i(JIT_V1, base);
+  jit_movi_p(JIT_R0, count);
+  (void)jit_calli(sjc.struct_raw_refs_code);
+  ref2 = jit_jmpi(jit_forward());
+  mz_patch_branch(ref);
+  (void)jit_beqi_i(refslow, JIT_R2, scheme_proc_chaperone_type);
+  CHECK_LIMIT();
+
+  /* This is the fast path: */
+  for (i = 0; i < count; i++) {
+    jit_ldxi_p(JIT_R1, JIT_R0, (intptr_t)&(((Scheme_Structure *)0x0)->slots[i+base]));
+    if (i != count - 1)
+      mz_rs_stxi(stack_pos+i, JIT_R1);
+    else
+      jit_movr_p(JIT_R0, JIT_R1);
+    CHECK_LIMIT();
+  }
+
+  mz_patch_branch(ref2);
+  __END_SHORT_JUMPS__(1);
+
+  return 1;
+}
+
 #endif
diff --git a/racket/src/racket/src/jitcommon.c b/racket/src/racket/src/jitcommon.c
index 11ca5ba8e8..ff88696c91 100644
--- a/racket/src/racket/src/jitcommon.c
+++ b/racket/src/racket/src/jitcommon.c
@@ -182,6 +182,21 @@ static void chaperone_set_mark()
   MZ_RUNSTACK[1] = SCHEME_CHAPERONE_VAL(MZ_RUNSTACK[1]);
 }
 
+static Scheme_Object *unsafe_struct_refs(Scheme_Object **rs, int offset, int count)
+{
+  int i;
+  Scheme_Object *v, *s = rs[0];
+
+  for (i = 0; i < count; i++) {
+    v = scheme_struct_ref(s, offset + i);
+    if (i == count-1)
+      return v;
+    rs[i] = v;
+  }
+
+  return NULL;
+}
+
 #define JITCOMMON_TS_PROCS
 #include "jit_ts.c"
 
@@ -1824,6 +1839,29 @@ static int common4(mz_jit_state *jitter, void *_data)
     scheme_jit_register_sub_func(jitter, code, scheme_false);
   }
 
+  /* *** struct_raw_refs_code *** */
+  /* R1 points into the runstack, *R1 is struct, R0 is
+     count >= 2, and V1 is a starting slot in the structure */
+  {
+    void *code;
+
+    code = jit_get_ip();
+    
+    sjc.struct_raw_refs_code = code;
+
+    mz_prolog(JIT_R2);
+    JIT_UPDATE_THREAD_RSPTR();
+    jit_prepare(3);
+    jit_pusharg_p(JIT_R0);
+    jit_pusharg_p(JIT_V1);
+    jit_pusharg_p(JIT_R1);
+    (void)mz_finish_lwe(ts_unsafe_struct_refs, ref);
+    jit_retval(JIT_R0);
+    mz_epilog(JIT_R2);
+
+    scheme_jit_register_sub_func(jitter, code, scheme_false);
+  }
+
   /* *** syntax_e_code *** */
   /* R0 is (potential) syntax object */
   {