diff --git a/pkgs/games/crafty/default.nix b/pkgs/games/crafty/default.nix
index e0eb49b53cb8..54deae2ecfe1 100644
--- a/pkgs/games/crafty/default.nix
+++ b/pkgs/games/crafty/default.nix
@@ -661,6 +661,7 @@ stdenv.mkDerivation rec {
     homepage = http://www.craftychess.com/;
     description = "Crafty is a free, open-source computer chess program developed by Dr. Robert M. Hyatt";
     license = stdenv.lib.licenses.unfree;
+    platforms = stdenv.lib.platforms.unix;
     maintainers = [ stdenv.lib.maintainers.jwiegley ];
   };
 }