diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 51b02eab03..a26e7e448a 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -519,7 +519,7 @@ class Formula
       "linked_keg" => (linked_keg.realpath.basename.to_s if linked_keg.exist?),
       "keg_only" => keg_only?,
       "dependencies" => deps.map {|dep| dep.to_s},
-      "conflicts_with" => conflicts.map {|c| c.formula},
+      "conflicts_with" => conflicts.map(&:name),
       "options" => [],
       "caveats" => caveats
     }