diff --git a/ChangeLog b/ChangeLog
index 4dd394b99f..5c0d63ac1f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Aug  7 19:29:26 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (dbl2big): A condition simplified.
+
 Wed Aug  7 16:34:30 2013  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* test/webrick/test_cgi.rb (TestWEBrickCGI#{start_cgi_server,test_cgi}):
diff --git a/bignum.c b/bignum.c
index cfd8a0a820..d3c0f7747b 100644
--- a/bignum.c
+++ b/bignum.c
@@ -4749,7 +4749,7 @@ dbl2big(double d)
 	rb_raise(rb_eFloatDomainError, "NaN");
     }
 
-    while (!POSFIXABLE(u) || 0 != (long)u) {
+    while (1.0 <= u) {
 	u /= (double)(BIGRAD);
 	i++;
     }