diff --git a/test/rdoc/helper.rb b/test/rdoc/helper.rb
index f22e4162ee..743c6d8fed 100644
--- a/test/rdoc/helper.rb
+++ b/test/rdoc/helper.rb
@@ -203,6 +203,5 @@ class RDoc::TestCase < Test::Unit::TestCase
     end
   end
 
-  alias capture_io capture_output
   alias skip omit
 end