diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 09f7641dc9d9..df5dfaa554bc 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -741,7 +741,7 @@ in
             + "'boot.loader.grub.mirroredBoots' to make the system bootable.";
         }
         {
-          assertion = cfg.efiSupport || all (c: c < 2) (mapAttrsToList (_: c: c) bootDeviceCounters);
+          assertion = cfg.efiSupport || all (c: c < 2) (mapAttrsToList (n: c: if n == "nodev" then 0 else c) bootDeviceCounters);
           message = "You cannot have duplicated devices in mirroredBoots";
         }
         {