diff --git a/Library/Homebrew/os/mac/xcode.rb b/Library/Homebrew/os/mac/xcode.rb
index 7733d44088..c5b7b34385 100644
--- a/Library/Homebrew/os/mac/xcode.rb
+++ b/Library/Homebrew/os/mac/xcode.rb
@@ -130,11 +130,11 @@ module OS
       end
 
       def provides_gcc?
-        version < "4.3"
+        installed? && version < "4.3"
       end
 
       def provides_cvs?
-        version < "5.0"
+        installed? && version < "5.0"
       end
 
       def default_prefix?