diff --git a/ChangeLog b/ChangeLog
index 9270ed6574..96f2879a41 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jun  6 10:58:23 2007  Koichi Sasada  <ko1@atdot.net>
+
+	* eval.c (rb_yield): fix to check Qundef.
+
 Wed Jun  6 10:57:45 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* test/ruby/test_continuation.rb: add a test for last commit.
diff --git a/eval.c b/eval.c
index 38c8b84cdc..0c6aceee7e 100644
--- a/eval.c
+++ b/eval.c
@@ -914,7 +914,12 @@ VALUE
 rb_yield(VALUE val)
 {
     volatile VALUE tmp = val;
-    tmp = rb_yield_0(1, &val);
+    if (val == Qundef) {
+	tmp = rb_yield_0(0, 0);
+    }
+    else {
+	tmp = rb_yield_0(1, &val);
+    }
     return tmp;
 }