diff --git a/pkgs/development/libraries/tk/generic.nix b/pkgs/development/libraries/tk/generic.nix
index 87a2edee3ca2..2258f28b9c48 100644
--- a/pkgs/development/libraries/tk/generic.nix
+++ b/pkgs/development/libraries/tk/generic.nix
@@ -16,6 +16,7 @@ stdenv.mkDerivation {
 
   postInstall = ''
     ln -s $out/bin/wish* $out/bin/wish
+    cp ../{unix,generic}/*.h $out/include
   '';
 
   configureFlags = [