diff --git a/src/mzscheme/src/jit.c b/src/mzscheme/src/jit.c
index 6810b1b05c..69e9efaff0 100644
--- a/src/mzscheme/src/jit.c
+++ b/src/mzscheme/src/jit.c
@@ -1957,16 +1957,18 @@ static jit_insn *generate_proc_struct_retry(mz_jit_state *jitter, int num_rands,
 #if 1
 # define mz_prepare_direct_prim(n) mz_prepare(n)
 # define mz_finishr_direct_prim(reg, proc) mz_finishr(reg)
+# define mz_direct_only(p) p
 #else
-# define mz_prepare_direct_prim(n) mz_prepare(n+1)
+# define mz_prepare_direct_prim(n) mz_prepare(n)
 # define mz_finishr_direct_prim(reg, proc) (jit_pusharg_p(reg), (void)mz_finish(proc))
-static Scheme_Object *noncm_prim_indirect(Scheme_Prim proc, int argc, Scheme_Object **argv)
+# define mz_direct_only(p) /* skip this arg, so that total count <= 3 args */
+static Scheme_Object *noncm_prim_indirect(Scheme_Prim proc, int argc)
 {
-  return proc(argc, argv);
+  return proc(argc, MZ_RUNSTACK);
 }
-static Scheme_Object *prim_indirect(Scheme_Primitive_Closure_Proc proc, int argc, Scheme_Object **argv, Scheme_Object *self)
+static Scheme_Object *prim_indirect(Scheme_Primitive_Closure_Proc proc, int argc, Scheme_Object *self)
 {
-  return proc(argc, argv, self);
+  return proc(argc, MZ_RUNSTACK, self);
 }
 #endif
 
@@ -1985,7 +1987,7 @@ static int generate_direct_prim_tail_call(mz_jit_state *jitter, int num_rands)
   jit_movi_i(JIT_R1, num_rands);
   mz_prepare_direct_prim(2); /* a prim takes 3 args, but a NONCM prim ignores the 3rd */
   CHECK_LIMIT();
-  jit_pusharg_p(JIT_RUNSTACK);
+  mz_direct_only(jit_pusharg_p(JIT_RUNSTACK));
   jit_pusharg_i(JIT_R1);
   mz_finishr_direct_prim(JIT_V1, noncm_prim_indirect);
   CHECK_LIMIT();
@@ -2178,7 +2180,7 @@ static int generate_direct_prim_non_tail_call(mz_jit_state *jitter, int num_rand
   jit_movi_i(JIT_R1, num_rands);
   mz_prepare_direct_prim(2); /* a prim takes 3 args, but a NONCM prim ignores the 3rd */
   CHECK_LIMIT();
-  jit_pusharg_p(JIT_RUNSTACK);
+  mz_direct_only(jit_pusharg_p(JIT_RUNSTACK));
   jit_pusharg_i(JIT_R1);
   mz_finishr_direct_prim(JIT_V1, noncm_prim_indirect);
   CHECK_LIMIT();
@@ -2471,7 +2473,7 @@ static int generate_non_tail_call(mz_jit_state *jitter, int num_rands, int direc
     mz_prepare_direct_prim(3);
     jit_pusharg_p(JIT_V1);
     if (num_rands < 0) { jit_movr_p(JIT_V1, JIT_R0); } /* save argc to manually pop runstack */
-    jit_pusharg_p(JIT_RUNSTACK);
+    mz_direct_only(jit_pusharg_p(JIT_RUNSTACK));
     jit_pusharg_i(JIT_R2);
     mz_finishr_direct_prim(JIT_R1, prim_indirect);
     CHECK_LIMIT();
@@ -7207,7 +7209,7 @@ static int do_generate_common(mz_jit_state *jitter, void *_data)
       }
       JIT_UPDATE_THREAD_RSPTR();
       mz_prepare_direct_prim(2);
-      jit_pusharg_p(JIT_RUNSTACK);
+      mz_direct_only(jit_pusharg_p(JIT_RUNSTACK));
       jit_pusharg_p(JIT_R1);
       mz_finishr_direct_prim(JIT_R2, noncm_prim_indirect);
       CHECK_LIMIT();