diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 57bf2cefa6f4..8ba7ae2c7fa2 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -212,7 +212,7 @@ in
 
       fsIdentifier = mkOption {
         default = "uuid";
-        type = types.addCheck types.string
+        type = types.addCheck types.str
           (type: type == "uuid" || type == "label" || type == "provided");
         description = ''
           Determines how grub will identify devices when generating the