diff --git a/mrbgems/mruby-rational/mrblib/rational.rb b/mrbgems/mruby-rational/mrblib/rational.rb
index 54324b05f..37dcfc2a0 100644
--- a/mrbgems/mruby-rational/mrblib/rational.rb
+++ b/mrbgems/mruby-rational/mrblib/rational.rb
@@ -69,7 +69,7 @@ class Rational < Numeric
   end
 end
 
-class << Numeric
+class Numeric
   def to_r
     Rational(self, 1)
   end