diff --git a/pkgs/development/compilers/gcc/4.9/default.nix b/pkgs/development/compilers/gcc/4.9/default.nix
index 02747d90567..7de8a140c0a 100644
--- a/pkgs/development/compilers/gcc/4.9/default.nix
+++ b/pkgs/development/compilers/gcc/4.9/default.nix
@@ -475,7 +475,7 @@ stdenv.mkDerivation ({
     else null;
 
   passthru =
-    { inherit langC langCC langAda langFortran langVhdl langGo enableMultilib version; };
+    { inherit langC langCC langAda langFortran langVhdl langGo enableMultilib version; isGNU = true; };
 
   inherit enableParallelBuilding;