diff --git a/nixos/modules/programs/xss-lock.nix b/nixos/modules/programs/xss-lock.nix
index 1bb73905599f..7a556e41061c 100644
--- a/nixos/modules/programs/xss-lock.nix
+++ b/nixos/modules/programs/xss-lock.nix
@@ -42,5 +42,10 @@ in
         ]);
       serviceConfig.Restart = "always";
     };
+
+    warnings = lib.mkIf (config.services.xserver.displayManager.startx.enable) [
+      "xss-lock service only works if a displayManager is set; it doesn't work when services.xserver.displayManager.startx.enable = true"
+    ];
+
   };
 }