diff --git a/pkgs/development/libraries/tk/8.4.16.nix b/pkgs/development/libraries/tk/8.4.16.nix
index c43e53cc8279..1f26db83f1b3 100644
--- a/pkgs/development/libraries/tk/8.4.16.nix
+++ b/pkgs/development/libraries/tk/8.4.16.nix
@@ -7,7 +7,7 @@ stdenv.mkDerivation {
     sha256 = "0cciavzd05bpm5yfppid0s0vsf8kabwia9620vgvi26sv1gjgwhb";
   };
   postInstall = ''
-    echo -e '#! /bin/sh \n $( readlink -f $( which wish${__substring 0 3 version}) ) "$@"' >$out/bin/wish
+    echo -e '#! /bin/sh \n $( readlink -f $( type -tP wish${__substring 0 3 version}) ) "$@"' >$out/bin/wish
     chmod a+x $out/bin/wish
   ''; 
   configureFlags="--with-tcl=${tcl}/lib";