diff --git a/pkgs/development/libraries/haskell/gtk-traymanager/default.nix b/pkgs/development/libraries/haskell/gtk-traymanager/default.nix
index 8d319ee246e..f55d9f2edef 100644
--- a/pkgs/development/libraries/haskell/gtk-traymanager/default.nix
+++ b/pkgs/development/libraries/haskell/gtk-traymanager/default.nix
@@ -1,11 +1,11 @@
-{ cabal, glib, gtk, X11 }:
+{ cabal, glib, gtk, x11 }:
 
 cabal.mkDerivation (self: {
   pname = "gtk-traymanager";
   version = "0.1.3";
   sha256 = "07671f3j3r07djgvrlpbdaqqnm2yc7sc5f5isjn5nczrwh8n0sj4";
   buildDepends = [ glib gtk ];
-  pkgconfigDepends = [ gtk X11 ];
+  pkgconfigDepends = [ gtk x11 ];
   meta = {
     homepage = "http://github.com/travitch/gtk-traymanager";
     description = "A wrapper around the eggtraymanager library for Linux system trays";