diff --git a/ChangeLog b/ChangeLog
index 310f6250a3..1a49e9b2ed 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jun 27 21:01:32 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* class.c (class_instance_method_list): m_tbl in prepended
+	  class/module is NULL.  [ruby-core:45915][Bug #6655]
+
 Wed Jun 27 16:48:48 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* class.c (rb_prepend_module): prepend module into another module.
diff --git a/class.c b/class.c
index fc3b483735..099f016d97 100644
--- a/class.c
+++ b/class.c
@@ -925,7 +925,7 @@ class_instance_method_list(int argc, VALUE *argv, VALUE mod, int obj, int (*func
 
     list = st_init_numtable();
     for (; mod; mod = RCLASS_SUPER(mod)) {
-	st_foreach(RCLASS_M_TBL(mod), method_entry_i, (st_data_t)list);
+	if (RCLASS_M_TBL(mod)) st_foreach(RCLASS_M_TBL(mod), method_entry_i, (st_data_t)list);
 	if (BUILTIN_TYPE(mod) == T_ICLASS) continue;
 	if (obj && FL_TEST(mod, FL_SINGLETON)) continue;
 	if (!recur) break;
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index decb217289..5826ed0269 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -1270,4 +1270,9 @@ class TestModule < Test::Unit::TestCase
     expected = [:M2,[:M3,[:C1,[:M4,[:M1,[:C0,[:M0],:C0],:M1],:M4],:C1],:M3],:M2]
     assert_equal(expected, obj.m1)
   end
+
+  def test_prepend_instance_methods
+    bug6655 = '[ruby-core:45915]'
+    assert_equal(Object.instance_methods, Class.new {prepend Module.new}.instance_methods, bug6655)
+  end
 end