diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index b29df1cba6..c18fb59a13 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -70,12 +70,12 @@ class Formula
 
   def determine_active_spec
     case
-    when @head && ARGV.build_head?        then @head    # --HEAD
-    when @devel && ARGV.build_devel?      then @devel   # --devel
-    when @bottle && install_bottle?(self) then @bottle  # bottle available
-    when @stable                          then @stable
-    when @devel && @stable.nil?           then @devel   # devel-only
-    when @head && @stable.nil?            then @head    # head-only
+    when head && ARGV.build_head?        then head    # --HEAD
+    when devel && ARGV.build_devel?      then devel   # --devel
+    when bottle && install_bottle?(self) then bottle  # bottle available
+    when stable                          then stable
+    when devel && stable.nil?            then devel   # devel-only
+    when head && stable.nil?             then head    # head-only
     else
       raise FormulaSpecificationError, "formulae require at least a URL"
     end