diff --git a/nixos/modules/programs/wayland/gtklock.nix b/nixos/modules/programs/wayland/gtklock.nix
index a3cef937ca83..e1162ad99a64 100644
--- a/nixos/modules/programs/wayland/gtklock.nix
+++ b/nixos/modules/programs/wayland/gtklock.nix
@@ -39,7 +39,7 @@ in
     };
 
     style = mkOption {
-      type = with types; nullOr str;
+      type = with types; nullOr lines;
       default = null;
       description = ''
         CSS Stylesheet for gtklock.