diff --git a/nixos/modules/config/system-path.nix b/nixos/modules/config/system-path.nix
index 8dd92dd96af948..932e4ccca05020 100644
--- a/nixos/modules/config/system-path.nix
+++ b/nixos/modules/config/system-path.nix
@@ -60,6 +60,7 @@ in
     environment = {
 
       systemPackages = mkOption {
+        type = types.listOf types.path;
         default = [];
         example = "[ pkgs.icecat3 pkgs.thunderbird ]";
         description = ''
@@ -74,6 +75,7 @@ in
       };
 
       pathsToLink = mkOption {
+        type = types.listOf types.str;
         # Note: We need `/lib' to be among `pathsToLink' for NSS modules
         # to work.
         default = [];
diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 947328c2ff6a79..e18a1d4c112ca1 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -247,7 +247,7 @@ in
       # set at once.
       system.boot.loader.id = "grub";
 
-      environment.systemPackages = [ grub ];
+      environment.systemPackages = optional (grub != null) grub;
 
       boot.loader.grub.extraPrepareConfig =
         concatStrings (mapAttrsToList (n: v: ''