diff --git a/ChangeLog b/ChangeLog
index da7cf89a52..03aa2e634e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+Thu Sep 27 18:36:51 2012  Shugo Maeda  <shugo@ruby-lang.org>
+
+	* eval.c (rb_overlay_module, rb_mod_refine): accept a module as the
+	  argument of Module#refine.
+
+	* vm_method.c (search_method): if klass is an iclass, lookup the
+	  original module of the iclass in omod in order to allow
+	  refinements of modules.
+
+	* test/ruby/test_refinement.rb: add tests for the above changes.
+
 Thu Sep 27 18:12:20 2012  Aaron Patterson <aaron@tenderlovemaking.com>
 
 	* ext/syslog/lib/syslog/logger.rb: add a formatter to the
diff --git a/eval.c b/eval.c
index 9630ca2621..4d27a8ec6b 100644
--- a/eval.c
+++ b/eval.c
@@ -1030,12 +1030,22 @@ rb_mod_prepend(int argc, VALUE *argv, VALUE module)
     return module;
 }
 
+static
+void check_class_or_module(VALUE obj)
+{
+    if (!RB_TYPE_P(obj, T_CLASS) && !RB_TYPE_P(obj, T_MODULE)) {
+	VALUE str = rb_inspect(obj);
+	rb_raise(rb_eTypeError, "%s is not a class/module",
+		 StringValuePtr(str));
+    }
+}
+
 void
 rb_overlay_module(NODE *cref, VALUE klass, VALUE module)
 {
     VALUE iclass, c, superclass = klass;
 
-    Check_Type(klass, T_CLASS);
+    check_class_or_module(klass);
     Check_Type(module, T_MODULE);
     if (NIL_P(cref->nd_omod)) {
 	cref->nd_omod = rb_hash_new();
@@ -1184,7 +1194,7 @@ rb_mod_refine(VALUE module, VALUE klass)
     ID id_overlaid_modules, id_refined_class;
     VALUE overlaid_modules;
 
-    Check_Type(klass, T_CLASS);
+    check_class_or_module(klass);
     CONST_ID(id_overlaid_modules, "__overlaid_modules__");
     overlaid_modules = rb_attr_get(module, id_overlaid_modules);
     if (NIL_P(overlaid_modules)) {
diff --git a/test/ruby/test_refinement.rb b/test/ruby/test_refinement.rb
index cc460894c4..ac6df929f0 100644
--- a/test/ruby/test_refinement.rb
+++ b/test/ruby/test_refinement.rb
@@ -324,5 +324,61 @@ class TestRefinement < Test::Unit::TestCase
     obj = c.new
     assert_equal([:c, :m1, :m2], m2.module_eval { obj.foo })
   end
-end
 
+  def test_refine_module_without_overriding
+    m1 = Module.new
+    c = Class.new {
+      include m1
+    }
+    m2 = Module.new {
+      refine m1 do
+        def foo
+          :m2
+        end
+      end
+    }
+    obj = c.new
+    assert_equal(:m2, m2.module_eval { obj.foo })
+  end
+
+  def test_refine_module_with_overriding
+    m1 = Module.new {
+      def foo
+        [:m1]
+      end
+    }
+    c = Class.new {
+      include m1
+    }
+    m2 = Module.new {
+      refine m1 do
+        def foo
+          super << :m2
+        end
+      end
+    }
+    obj = c.new
+    assert_equal([:m1, :m2], m2.module_eval { obj.foo })
+  end
+
+  def test_refine_neither_class_nor_module
+    assert_raise(TypeError) do
+      Module.new {
+        refine Object.new do
+        end
+      }
+    end
+    assert_raise(TypeError) do
+      Module.new {
+        refine 123 do
+        end
+      }
+    end
+    assert_raise(TypeError) do
+      Module.new {
+        refine "foo" do
+        end
+      }
+    end
+  end
+end
diff --git a/vm_method.c b/vm_method.c
index 43b9ddb107..bf605e6f67 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -385,10 +385,20 @@ search_method(VALUE klass, ID id, VALUE omod, VALUE *defined_class_ptr)
     for (body = 0; klass; klass = RCLASS_SUPER(klass)) {
 	st_table *m_tbl;
 
-	if (!NIL_P(omod) && klass != skipped_class &&
-	    !NIL_P(iclass = rb_hash_lookup(omod, klass))) {
-	    skipped_class = klass;
-	    klass = iclass;
+	if (!NIL_P(omod) && klass != skipped_class) {
+	    VALUE c;
+
+	    if (BUILTIN_TYPE(klass) == T_ICLASS) {
+		c = RBASIC(klass)->klass;
+	    }
+	    else {
+		c = klass;
+	    }
+	    iclass = rb_hash_lookup(omod, c);
+	    if (!NIL_P(iclass)) {
+		skipped_class = klass;
+		klass = iclass;
+	    }
 	}
 	m_tbl = RCLASS_M_TBL(klass);
 	if (!m_tbl) {