diff --git a/ChangeLog b/ChangeLog
index 2a4aab707e..2335d02654 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Mar 29 17:38:24 2010  Keiju Ishitsuka  <keiju@ruby-lang.org>
+
+	* ext/rational/lib/rational.rb: fix [Bug #1397].
+
 Fri Mar 26 13:09:12 2010  Akinori MUSHA  <knu@iDaemons.org>
 
 	* eval.c (rb_eval): Use for() and make it a bit easier to read and
diff --git a/ext/rational/lib/rational.rb b/ext/rational/lib/rational.rb
index cf8e90b2c1..65d8c44110 100644
--- a/ext/rational/lib/rational.rb
+++ b/ext/rational/lib/rational.rb
@@ -383,7 +383,7 @@ class Rational < Numeric
   # Converts the rational to a Float.
   #
   def to_f
-    @numerator.to_f/@denominator.to_f
+    @numerator.fdiv(@denominator)
   end
 
   #