diff --git a/ChangeLog b/ChangeLog
index fba82c0db8..c52d28ebb7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue May 17 21:24:04 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* thread.c (rb_mutex_lock): remove remove_signal_thread_list() call.
+	  It's meaningless because lock_interrupt doesn't call
+	  add_signal_thread_list().
+
 Tue May 17 20:20:49 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* vm_core.h (rb_thread_struct): add volatile to
diff --git a/thread.c b/thread.c
index 6f7118de47..8ec6d9bafb 100644
--- a/thread.c
+++ b/thread.c
@@ -3535,7 +3535,6 @@ rb_mutex_lock(VALUE self)
 		interrupted = lock_func(th, mutex, timeout_ms);
 	    });
 	    th->transition_for_lock = 0;
-	    remove_signal_thread_list(th);
 	    reset_unblock_function(th, &oldubf);
 
 	    th->locking_mutex = Qfalse;