diff --git a/nixos/modules/services/x11/display-managers/lightdm-greeters/gtk.nix b/nixos/modules/services/x11/display-managers/lightdm-greeters/gtk.nix
index de932e6e840..9c1dc1d1c12 100644
--- a/nixos/modules/services/x11/display-managers/lightdm-greeters/gtk.nix
+++ b/nixos/modules/services/x11/display-managers/lightdm-greeters/gtk.nix
@@ -88,6 +88,7 @@ in
       cursorTheme = {
 
         package = mkOption {
+          type = types.package;
           default = pkgs.gnome3.adwaita-icon-theme;
           defaultText = "pkgs.gnome3.adwaita-icon-theme";
           description = ''