diff --git a/ChangeLog b/ChangeLog
index 2065b0d0da..c0f734922d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jun 20 22:49:27 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (bignorm): Don't call bigtrunc if the result is a fixnum.
+
 Thu Jun 20 22:29:42 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (rb_uint2big): Refactored.
diff --git a/bignum.c b/bignum.c
index b0dc48c59b..be9c1e2740 100644
--- a/bignum.c
+++ b/bignum.c
@@ -322,7 +322,9 @@ static VALUE
 bignorm(VALUE x)
 {
     if (RB_TYPE_P(x, T_BIGNUM)) {
-	x = bigfixize(bigtrunc(x));
+	x = bigfixize(x);
+        if (!FIXNUM_P(x))
+            bigtrunc(x);
     }
     return x;
 }