diff --git a/src/mzscheme/src/jit.c b/src/mzscheme/src/jit.c
index e8d72f1db8..513657162e 100644
--- a/src/mzscheme/src/jit.c
+++ b/src/mzscheme/src/jit.c
@@ -5361,6 +5361,10 @@ static int do_generate_common(mz_jit_state *jitter, void *_data)
 	}
 	jit_ldxi_s(JIT_R2, JIT_R0, &((Scheme_Object *)0x0)->type);
 	(void)jit_bnei_i(reffail, JIT_R2, ty);
+        if (iii) {
+          jit_ldxi_s(JIT_R2, JIT_R0, &(MZ_OPT_HASH_KEY((Scheme_Inclhash_Object *)0x0)));
+          (void)jit_bmsi_ul(reffail, JIT_R2, 0x1);
+        }
 	jit_ldxi_i(JIT_R2, JIT_R0, count_offset);
 	if (i) {
 	  /* index from expression: */
diff --git a/src/mzscheme/src/string.c b/src/mzscheme/src/string.c
index e7a695f88a..d29ffa62a4 100644
--- a/src/mzscheme/src/string.c
+++ b/src/mzscheme/src/string.c
@@ -615,9 +615,9 @@ scheme_init_string (Scheme_Env *env)
 			     env);
 
   scheme_add_global_constant("format",
-			     scheme_make_folding_prim(format,
-						      "format",
-						      1, -1, 1),
+			     scheme_make_noncm_prim(format,
+                                                    "format",
+                                                    1, -1),
 			     env);
   scheme_add_global_constant("printf",
 			     scheme_make_noncm_prim(sch_printf,