diff --git a/ChangeLog b/ChangeLog
index cd1c371bca..f27c99ea93 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Jun 26 01:18:13 2013  Masaya Tarui  <tarui@ruby-lang.org>
+
+	* gc.c (is_before_sweep): Add new helper function that check the object
+	  is before sweep?
+	* gc.c (rb_gc_force_recycle): Have to clear mark bit if object's slot
+	  already ready to mainor sweep.
+
 Wed Jun 26 01:17:29 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (bigsub_int): Fix a buffer over read.
diff --git a/gc.c b/gc.c
index e31602a77d..1f4afb0f00 100644
--- a/gc.c
+++ b/gc.c
@@ -603,6 +603,22 @@ RVALUE_PROMOTE(VALUE obj)
 #endif
 }
 
+static inline int
+is_before_sweep(VALUE obj)
+{
+    struct heaps_slot *slot;
+    rb_objspace_t *objspace = &rb_objspace;
+    if (is_lazy_sweeping(objspace)) {
+	slot = objspace->heap.sweep_slots;
+	while (slot) {
+	    if(slot->header == GET_HEAP_HEADER(obj))
+		return TRUE;
+	    slot = slot->next;
+	}
+    }
+    return FALSE;
+}
+
 static inline void
 RVALUE_DEMOTE(VALUE obj)
 {
@@ -3971,6 +3987,9 @@ rb_gc_force_recycle(VALUE p)
 #if USE_RGENGC
     CLEAR_IN_BITMAP(GET_HEAP_REMEMBERSET_BITS(p), p);
     CLEAR_IN_BITMAP(GET_HEAP_OLDGEN_BITS(p), p);
+    if(!is_before_sweep(p)){
+	CLEAR_IN_BITMAP(GET_HEAP_MARK_BITS(p), p);
+    }
 #endif
 
     objspace->total_freed_object_num++;