diff --git a/src/mzscheme/src/jit.c b/src/mzscheme/src/jit.c
index 7ccd3cb2ea..3b8fc635fd 100644
--- a/src/mzscheme/src/jit.c
+++ b/src/mzscheme/src/jit.c
@@ -6201,6 +6201,7 @@ static int generate(Scheme_Object *obj, mz_jit_state *jitter, int is_tail, int m
           jit_ldxi_p(JIT_R2, JIT_R2, WORDS_TO_BYTES(pos));
           CHECK_LIMIT();
 
+	  JIT_UPDATE_THREAD_RSPTR_IF_NEEDED();
           mz_prepare(1);
 	  jit_pusharg_p(JIT_R2);
 	  (void)mz_finish(make_global_ref);
diff --git a/src/mzscheme/src/struct.c b/src/mzscheme/src/struct.c
index f0cea1cedc..dfba030e55 100644
--- a/src/mzscheme/src/struct.c
+++ b/src/mzscheme/src/struct.c
@@ -737,6 +737,11 @@ static Scheme_Object *prop_pred(int argc, Scheme_Object **args, Scheme_Object *p
   Scheme_Struct_Type *stype;
   Scheme_Object *prop = SCHEME_PRIM_CLOSURE_ELS(prim)[0];
 
+  if (!args[0]) {
+    printf("%p\n", prim);
+    return scheme_false;
+  }
+
   if (SCHEME_STRUCTP(args[0]))
     stype = ((Scheme_Structure *)args[0])->stype;
   else if (SAME_TYPE(SCHEME_TYPE(args[0]), scheme_struct_type_type))