diff --git a/nixos/modules/system/activation/top-level.nix b/nixos/modules/system/activation/top-level.nix
index b0f77ca3fb8..75eb91f2834 100644
--- a/nixos/modules/system/activation/top-level.nix
+++ b/nixos/modules/system/activation/top-level.nix
@@ -173,6 +173,7 @@ in
           };
 
           options.configuration = mkOption {
+            type = types.attrsOf types.anything;
             default = {};
             description = "Arbitrary NixOS configuration options.";
           };