diff --git a/nixos/modules/hardware/video/ati.nix b/nixos/modules/hardware/video/ati.nix
index 033e49d2233..bf91bcf0776 100644
--- a/nixos/modules/hardware/video/ati.nix
+++ b/nixos/modules/hardware/video/ati.nix
@@ -18,6 +18,8 @@ in
 
   config = mkIf enabled {
 
+    nixpkgs.config.xorg.fglrxCompat = true;
+
     services.xserver.drivers = singleton
       { name = "fglrx"; modules = [ ati_x11 ]; libPath = [ "${ati_x11}/lib" ]; };
 
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index b1d657215f1..bdffa0f9f2c 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -10268,7 +10268,7 @@ in
     mesa = mesa_noglu;
     udev = if stdenv.isLinux then udev else null;
     libdrm = if stdenv.isLinux then libdrm else null;
-    fglrxCompat = false;
+    fglrxCompat = config.xorg.fglrxCompat or false; # `config` because we have no `xorg.override`
   } // { inherit xlibsWrapper; } );
 
   xwayland = callPackage ../servers/x11/xorg/xwayland.nix { };