diff --git a/pkgs/racket-pkgs/racket-doc/scribblings/reference/namespaces.scrbl b/pkgs/racket-pkgs/racket-doc/scribblings/reference/namespaces.scrbl
index 22ea7c2d14..05d05c0c11 100644
--- a/pkgs/racket-pkgs/racket-doc/scribblings/reference/namespaces.scrbl
+++ b/pkgs/racket-pkgs/racket-doc/scribblings/reference/namespaces.scrbl
@@ -309,7 +309,10 @@ Returns the @tech{module registry} of the given namespace. This value
 is useful only for identification via @racket[eq?].}
 
 
-@defproc[(module->namespace [modname module-path?]) namespace?]{
+@defproc[(module->namespace [mod (or/c module-path? 
+                                       resolved-module-path? 
+                                       module-path-index?)])
+         namespace?]{
 
 Returns a namespace that corresponds to the body of an instantiated
 module in the current namespace's @tech{module registry} and in the
diff --git a/racket/src/racket/src/module.c b/racket/src/racket/src/module.c
index 6da109787d..537c652654 100644
--- a/racket/src/racket/src/module.c
+++ b/racket/src/racket/src/module.c
@@ -3121,7 +3121,14 @@ Scheme_Object *scheme_module_to_namespace(Scheme_Object *name, Scheme_Env *env)
   Scheme_Env *menv;
   Scheme_Object *modchain;
 
-  name = scheme_module_resolve(scheme_make_modidx(name, scheme_false, scheme_false), 1);
+  if (SCHEME_MODNAMEP(name)) {
+    ;
+  } else if (SAME_TYPE(SCHEME_TYPE(name), scheme_module_index_type)) {
+    name = scheme_module_resolve(name, 1);
+  } else {
+    /* name is path or module-path */
+    name = scheme_module_resolve(scheme_make_modidx(name, scheme_false, scheme_false), 1);
+  }
 
   menv = get_special_modenv(name);
   if (!menv) {
@@ -3163,8 +3170,11 @@ static Scheme_Object *module_to_namespace(int argc, Scheme_Object *argv[])
 
   env = scheme_get_env(NULL);
 
-  if (!scheme_is_module_path(argv[0]))
-    scheme_wrong_contract("module->namespace", "module-path?", 0, argc, argv);
+  if (!SCHEME_PATHP(argv[0])
+      && !SCHEME_MODNAMEP(argv[0])
+      && !SAME_TYPE(SCHEME_TYPE(argv[0]), scheme_module_index_type)
+      && !scheme_is_module_path(argv[0]))
+    scheme_wrong_contract("module->namespace", "(or/c module-path? module-path-index? resolved-module-path?)", 0, argc, argv);
 
   return scheme_module_to_namespace(argv[0], env);
 }