diff --git a/pkgs/racket-test/tests/racket/optimize.rktl b/pkgs/racket-test/tests/racket/optimize.rktl
index 4f69af851e..44b841a5db 100644
--- a/pkgs/racket-test/tests/racket/optimize.rktl
+++ b/pkgs/racket-test/tests/racket/optimize.rktl
@@ -2271,6 +2271,7 @@
   (test-pred 'impersonator?)
   (test-pred 'procedure?)
   (test-pred 'eof-object?)
+  (test-pred 'immutable?)
   (test-pred 'not))
 
 (let ([test-bin
diff --git a/racket/src/racket/src/list.c b/racket/src/racket/src/list.c
index 4018d18b62..db85b1f354 100644
--- a/racket/src/racket/src/list.c
+++ b/racket/src/racket/src/list.c
@@ -272,11 +272,9 @@ scheme_init_list (Scheme_Env *env)
                                                             | SCHEME_PRIM_IS_OMITABLE);
   scheme_add_global_constant ("list*", p, env);
 
-  scheme_add_global_constant("immutable?",
-			     scheme_make_folding_prim(immutablep,
-						      "immutable?",
-						      1, 1, 1),
-			     env);
+  p = scheme_make_folding_prim(immutablep, "immutable?", 1, 1, 1);
+  SCHEME_PRIM_PROC_FLAGS(p) |= scheme_intern_prim_opt_flags(SCHEME_PRIM_IS_OMITABLE);
+  scheme_add_global_constant("immutable?", p, env);
 
   p = scheme_make_immed_prim(length_prim, "length", 1, 1);
   SCHEME_PRIM_PROC_FLAGS(p) |= scheme_intern_prim_opt_flags(SCHEME_PRIM_IS_UNARY_INLINED);