diff --git a/src/racket/src/fun.c b/src/racket/src/fun.c
index 071c99259c..3052129f49 100644
--- a/src/racket/src/fun.c
+++ b/src/racket/src/fun.c
@@ -4182,7 +4182,7 @@ Scheme_Object *scheme_apply_chaperone(Scheme_Object *o, int argc, Scheme_Object
   if ((c == argc) || (c == (argc + 1))) {
     if (c > argc) {
       post = argv2[0];
-      memmove(argv2, argv2 + 1, sizeof(Scheme_Object*)*c);
+      memmove(argv2, argv2 + 1, sizeof(Scheme_Object*)*argc);
     } else
       post = NULL;
     for (i = 0; i < argc; i++) {
@@ -4229,10 +4229,10 @@ Scheme_Object *scheme_apply_chaperone(Scheme_Object *o, int argc, Scheme_Object
       return scheme_tail_apply(px->prev, c, argv2);
     }
   } else {
-    /* Last element is a filter for the result(s) */
+    /* First element is a filter for the result(s) */
     if (!SCHEME_PROCP(post))
       scheme_raise_exn(MZEXN_FAIL_CONTRACT,
-                       "procedure chaperone: %V: expected <procedure> as last result, produced: %V",
+                       "procedure chaperone: %V: expected <procedure> as first result, produced: %V",
                        px->redirects,
                        post);
     if (auto_val) {
diff --git a/src/racket/src/jit.c b/src/racket/src/jit.c
index 494ca0e9cb..6fd38c94d9 100644
--- a/src/racket/src/jit.c
+++ b/src/racket/src/jit.c
@@ -6767,7 +6767,7 @@ static int generate_inlined_unary(mz_jit_state *jitter, Scheme_App2_Rec *app, in
 
       mz_runstack_unskipped(jitter, 1);
 
-      mz_rs_sync_fail_branch();
+      mz_rs_sync();
 
       __START_TINY_JUMPS__(1);
       ref = jit_bmci_ul(jit_forward(), JIT_R0, 0x1);
@@ -6815,6 +6815,8 @@ static int generate_inlined_unary(mz_jit_state *jitter, Scheme_App2_Rec *app, in
 
       mz_runstack_unskipped(jitter, 1);
 
+      mz_rs_sync();
+
       /* check for chaperone: */
       __START_TINY_JUMPS__(1);
       jit_ldxi_s(JIT_R1, JIT_R0, &((Scheme_Object *)0x0)->type);
@@ -8027,6 +8029,7 @@ static int generate_inlined_binary(mz_jit_state *jitter, Scheme_App3_Rec *app, i
 
       generate_two_args(app->rand1, app->rand2, jitter, 1, 2);
       CHECK_LIMIT();
+      mz_rs_sync();
       __START_TINY_JUMPS__(1);
       if (!unsafe)
         ref3 = jit_bmsi_ul(jit_forward(), JIT_R0, 0x1);
@@ -10979,6 +10982,7 @@ static int do_generate_common(mz_jit_state *jitter, void *_data)
   /* R0 is argument */
   unbox_code = jit_get_ip().ptr;
   mz_prolog(JIT_R1);
+  JIT_UPDATE_THREAD_RSPTR();
   jit_prepare(1);
   jit_pusharg_p(JIT_R0);
   (void)mz_finish(ts_scheme_unbox);
@@ -10991,6 +10995,7 @@ static int do_generate_common(mz_jit_state *jitter, void *_data)
   /* R0 is box, R1 is value */
   set_box_code = jit_get_ip().ptr;
   mz_prolog(JIT_R2);
+  JIT_UPDATE_THREAD_RSPTR();
   jit_prepare(2);
   jit_pusharg_p(JIT_R1);
   jit_pusharg_p(JIT_R0);