diff --git a/Library/Homebrew/formula_support.rb b/Library/Homebrew/formula_support.rb
index 9aa6358087..8b216db66f 100644
--- a/Library/Homebrew/formula_support.rb
+++ b/Library/Homebrew/formula_support.rb
@@ -60,7 +60,6 @@ class SoftwareSpec
   end
 
   def mirror val
-    @mirrors ||= []
     @mirrors << val
   end
 end