diff --git a/ChangeLog b/ChangeLog
index d5556b5cbb..d3261cd6fa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat Nov 14 21:54:46 2009  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* class.c (rb_mod_init_copy): fix memory leak of Class#dup.
+	  [ruby-dev:39687]
+
 Sat Nov 14 17:09:39 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (--with-opt-dir): ignore and suppress a warning.
diff --git a/class.c b/class.c
index a97494b8d7..056e1715be 100644
--- a/class.c
+++ b/class.c
@@ -151,6 +151,9 @@ rb_mod_init_copy(VALUE clone, VALUE orig)
     if (RCLASS_IV_TBL(orig)) {
 	ID id;
 
+	if (RCLASS_IV_TBL(clone)) {
+	    st_free_table(RCLASS_IV_TBL(clone));
+	}
 	RCLASS_IV_TBL(clone) = st_copy(RCLASS_IV_TBL(orig));
 	CONST_ID(id, "__classpath__");
 	st_delete(RCLASS_IV_TBL(clone), (st_data_t*)&id, 0);
@@ -159,6 +162,11 @@ rb_mod_init_copy(VALUE clone, VALUE orig)
     }
     if (RCLASS_M_TBL(orig)) {
 	struct clone_method_data data;
+
+	if (RCLASS_M_TBL(clone)) {
+	    extern void rb_free_m_table(st_table *tbl);
+	    rb_free_m_table(RCLASS_M_TBL(clone));
+	}
 	data.tbl = RCLASS_M_TBL(clone) = st_init_numtable();
 	data.klass = clone;
 	st_foreach(RCLASS_M_TBL(orig), clone_method,
diff --git a/gc.c b/gc.c
index f472bfc734..9de079be14 100644
--- a/gc.c
+++ b/gc.c
@@ -1459,8 +1459,8 @@ free_method_entry_i(ID key, rb_method_entry_t *me, st_data_t data)
     return ST_CONTINUE;
 }
 
-static void
-free_m_table(st_table *tbl)
+void
+rb_free_m_table(st_table *tbl)
 {
     st_foreach(tbl, free_method_entry_i, 0);
     st_free_table(tbl);
@@ -1988,7 +1988,7 @@ obj_free(rb_objspace_t *objspace, VALUE obj)
       case T_MODULE:
       case T_CLASS:
 	rb_clear_cache_by_class((VALUE)obj);
-	free_m_table(RCLASS_M_TBL(obj));
+	rb_free_m_table(RCLASS_M_TBL(obj));
 	if (RCLASS_IV_TBL(obj)) {
 	    st_free_table(RCLASS_IV_TBL(obj));
 	}