diff --git a/ChangeLog b/ChangeLog
index 35009540c0..e5c5c3daf0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Mon Mar 29 18:10:03 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/optparse.rb (Numeric): accept rationals.
+
 Mon Mar 29 15:10:39 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/tempfile.rb (Tempfile#open): re-open with same mode and
diff --git a/lib/optparse.rb b/lib/optparse.rb
index 24ec91d78e..b07d91ef6c 100644
--- a/lib/optparse.rb
+++ b/lib/optparse.rb
@@ -1531,9 +1531,16 @@ class OptionParser
 
   #
   # Generic numeric format, converts to Integer for integer format, Float
-  # for float format.
+  # for float format, and Rational for rational format.
   #
-  accept(Numeric, %r"\A[-+]?(?:#{octal}|#{float})"io) {|s,| eval(s) if s}
+  real = "[-+]?(?:#{octal}|#{float})"
+  accept(Numeric, /\A(#{real})(?:\/(#{real}))?/io) {|s, d, n|
+    if n
+      Rational(d, n)
+    elsif s
+      eval(s)
+    end
+  }
 
   #
   # Decimal integer format, to be converted to Integer.