diff --git a/ChangeLog b/ChangeLog
index 778420cc7a..29f775eb1f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Dec  8 13:51:41 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* eval.c (rb_yield_0): Qundef means no argument.  [ruby-Bugs-22525]
+
 Sun Dec  7 23:47:37 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* configure.in (LIBPATHFLAG): use numbered specifier if RPATHFLAG
diff --git a/eval.c b/eval.c
index dbcbb8e5af..c83bb2fc60 100644
--- a/eval.c
+++ b/eval.c
@@ -5060,7 +5060,7 @@ rb_yield_0(val, self, klass, flags, avalue)
 	    switch (node->nd_state) {
 	      case YIELD_FUNC_LAMBDA:
 		if (!avalue) {
-		    val = rb_ary_new3(1, val);
+		    val = (val == Qundef) ? rb_ary_new2(0) : rb_ary_new3(1, val);
 		}
 		break;
 	      case YIELD_FUNC_AVALUE: