diff --git a/nixos/modules/services/x11/xserver.nix b/nixos/modules/services/x11/xserver.nix
index 4dde4476d2c4..124f3eb3132e 100644
--- a/nixos/modules/services/x11/xserver.nix
+++ b/nixos/modules/services/x11/xserver.nix
@@ -358,6 +358,13 @@ in
         description = ''
           The contents of the configuration file of the X server
           (<filename>xorg.conf</filename>).
+
+          This option is set by multiple modules, and the configs are
+          concatenated together.
+
+          In Xorg configs the last config entries take precedence,
+          so you may want to use <literal>lib.mkAfter</literal> on this option
+          to override NixOS's defaults.
         '';
       };