diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 11e1eecb7e..66bf75d179 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -299,7 +299,9 @@ class Formula
   end
 
   def == other
-    instance_of?(other.class) && name == other.name
+    instance_of?(other.class) &&
+      name == other.name &&
+      active_spec == other.active_spec
   end
   alias_method :eql?, :==