diff --git a/modules/options.nix b/modules/options.nix
index c47f438..f255c99 100644
--- a/modules/options.nix
+++ b/modules/options.nix
@@ -21,12 +21,12 @@ in {
     };
 
     batteryDevice = mkOption {
-      type = types.nullOr types.string;
+      type = with types; nullOr (uniq str);
       default = null;
     };
 
     kbBacklightDevice = mkOption {
-      type = types.nullOr types.string;
+      type = with types; nullOr (uniq str);
       default = null;
     };