diff --git a/nixos/modules/config/timezone.nix b/nixos/modules/config/timezone.nix
index 068571393116..b9844b4adade 100644
--- a/nixos/modules/config/timezone.nix
+++ b/nixos/modules/config/timezone.nix
@@ -26,6 +26,7 @@ in
 
       hardwareClockInLocalTime = mkOption {
         default = false;
+        type = types.bool;
         description = "If set, keep the hardware clock in local time instead of UTC.";
       };