diff --git a/ChangeLog b/ChangeLog
index b8757622ca..f1c5858fc8 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Tue Oct  4 21:10:08 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* class.c (class_alloc): allocate extra memory after containing
+	  object setup to get rid of rare-but-potential memory leak.
+
+	* gc.c (gc_mark_children): skip marking extended members if ptr is
+	  NULL.
+
 Tue Oct  4 16:17:50 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* lib/time.rb (Time.strptime): use Time.at if d[:seconds] is set.
diff --git a/class.c b/class.c
index e6c1f8fd11..b595473333 100644
--- a/class.c
+++ b/class.c
@@ -49,10 +49,9 @@ static ID id_attached;
 static VALUE
 class_alloc(VALUE flags, VALUE klass)
 {
-    rb_classext_t *ext = ALLOC(rb_classext_t);
     NEWOBJ(obj, struct RClass);
     OBJSETUP(obj, klass, flags);
-    obj->ptr = ext;
+    obj->ptr = ALLOC(rb_classext_t);
     RCLASS_IV_TBL(obj) = 0;
     RCLASS_CONST_TBL(obj) = 0;
     RCLASS_M_TBL(obj) = 0;
diff --git a/gc.c b/gc.c
index c59c73696b..8840771c2f 100644
--- a/gc.c
+++ b/gc.c
@@ -1824,6 +1824,7 @@ gc_mark_children(rb_objspace_t *objspace, VALUE ptr, int lev)
       case T_CLASS:
       case T_MODULE:
 	mark_m_tbl(objspace, RCLASS_M_TBL(obj), lev);
+	if (!RCLASS_EXT(obj)) break;
 	mark_tbl(objspace, RCLASS_IV_TBL(obj), lev);
 	mark_const_tbl(objspace, RCLASS_CONST_TBL(obj), lev);
 	ptr = RCLASS_SUPER(obj);