diff --git a/ChangeLog b/ChangeLog
index aec6eb1c87..26f6fe5ead 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Jul  5 20:40:35 2009  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* complex.c (float_arg): returns PI for -0.0.
+
 Sun Jul  5 14:04:36 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* thread.c (rb_threadptr_exec_event_hooks): new function to
diff --git a/complex.c b/complex.c
index 048aa92bfd..d64c628128 100644
--- a/complex.c
+++ b/complex.c
@@ -1756,7 +1756,9 @@ float_arg(VALUE self)
 {
     if (isnan(RFLOAT_VALUE(self)))
 	return self;
-    return rb_call_super(0, 0);
+    if (f_tpositive_p(self))
+	return INT2FIX(0);
+    return rb_const_get(rb_mMath, id_PI);
 }
 
 /*