diff --git a/Library/Homebrew/extend/ENV/std.rb b/Library/Homebrew/extend/ENV/std.rb
index e931b33ba1..b45e34ccce 100644
--- a/Library/Homebrew/extend/ENV/std.rb
+++ b/Library/Homebrew/extend/ENV/std.rb
@@ -68,7 +68,7 @@ module Stdenv
       self.cxx = MacOS.locate("c++")
     end
 
-    if self['CC'] =~ GNU_GCC_REGEXP
+    if cc =~ GNU_GCC_REGEXP
       warn_about_non_apple_gcc($1)
     end