diff --git a/extras/modules.nix b/extras/modules.nix
index 98e9a96..3626a15 100644
--- a/extras/modules.nix
+++ b/extras/modules.nix
@@ -14,10 +14,10 @@ let
     then module: module
     else
       module:
-      # TODO: set key?
       {
         _class = class;
         _file = "${toString moduleLocation}#modules.${escapeNixIdentifier class}.${escapeNixIdentifier moduleName}";
+        key = "${toString moduleLocation}#modules.${escapeNixIdentifier class}.${escapeNixIdentifier moduleName}";
         imports = [ module ];
       };
 in
diff --git a/modules/nixosModules.nix b/modules/nixosModules.nix
index 737648d..6b0c9a7 100644
--- a/modules/nixosModules.nix
+++ b/modules/nixosModules.nix
@@ -18,6 +18,12 @@ in
         apply = mapAttrs (k: v: {
           _class = "nixos";
           _file = "${toString moduleLocation}#nixosModules.${k}";
+          # Note: this neglects to represent potential differences due to input
+          #       overrides or flake-parts extendModules. However, the cost for this
+          #       is too high or plain infeasible respectively. We choose to implement
+          #       deduplication and disabledModules regardless, because not doing
+          #       so poses a more direct problem.
+          key = "${toString moduleLocation}#nixosModules.${k}";
           imports = [ v ];
         });
         description = ''