diff --git a/lib/inventory/distributed-service/service-module.nix b/lib/inventory/distributed-service/service-module.nix
index b93554dcb..480cb3986 100644
--- a/lib/inventory/distributed-service/service-module.nix
+++ b/lib/inventory/distributed-service/service-module.nix
@@ -132,6 +132,11 @@ let
     in
     makeModuleExtensible (f args);
 
+  # Extend evalModules result by a module, returns .config.
+  extendEval =
+    eval: m:
+    (eval.extendModules { modules = lib.toList m; } ).config;
+
   /**
     Apply the settings to the instance
 
@@ -147,19 +152,19 @@ let
         # TODO: evaluate the settings against the interface
         # settings = (evalMachineSettings { inherit roleName instanceName; inherit (v) settings; }).config;
         settings = (
-          makeExtensibleConfig evalMachineSettings {
+          evalMachineSettings {
             inherit roleName instanceName machineName;
             inherit (v) settings;
           }
-        );
+        ).config;
       }) role.machines;
       # TODO: evaluate the settings against the interface
       settings = (
-        makeExtensibleConfig evalMachineSettings {
+        evalMachineSettings {
           inherit roleName instanceName;
           inherit (role) settings;
         }
-      );
+      ).config;
     }) instance.roles;
 in
 {
@@ -328,7 +333,14 @@ in
                             roles = lib.attrNames (lib.filterAttrs (_n: v: v.machines ? ${machineName}) roles);
                           };
                           settings = (
-                            makeExtensibleConfig evalMachineSettings {
+                            evalMachineSettings {
+                              inherit roleName instanceName machineName;
+                              settings =
+                                config.instances.${instanceName}.roles.${roleName}.machines.${machineName}.settings or { };
+                            }
+                          ).config;
+                          extendSettings = extendEval (
+                            evalMachineSettings {
                               inherit roleName instanceName machineName;
                               settings =
                                 config.instances.${instanceName}.roles.${roleName}.machines.${machineName}.settings or { };
@@ -396,6 +408,7 @@ in
                 in
                 uniqueStrings (collectRoles machineScope.instances);
             };
+            # TODO: instances.<instanceName>.roles should contain all roles, even if nobody has the role
             inherit (machineScope) instances;
 
             # There are no machine settings.
diff --git a/lib/inventory/distributed-service/tests/per_instance_args.nix b/lib/inventory/distributed-service/tests/per_instance_args.nix
index 3be840dd4..ad06ce855 100644
--- a/lib/inventory/distributed-service/tests/per_instance_args.nix
+++ b/lib/inventory/distributed-service/tests/per_instance_args.nix
@@ -23,16 +23,17 @@ let
       {
         instanceName,
         settings,
+        extendSettings,
         machine,
         roles,
         ...
       }:
       let
-        settings1 = settings {
+        finalSettings = extendSettings {
           # Sometimes we want to create a default settings set depending on the machine config.
           # Note: Other machines cannot depend on this settings. We must assign a new name to the settings.
           # And thus the new value is not accessible by other machines.
-          timeout = lib.mkOverride 10 "config.blah";
+          timeout = lib.mkOverride 10 "config.thing";
         };
       in
       {
@@ -46,12 +47,7 @@ let
 
           # We are double vendoring the settings
           # To test that we can do it indefinitely
-          vendoredSettings = settings1 {
-            # Sometimes we want to create a default settings set depending on the machine config.
-            # Note: Other machines cannot depend on this settings. We must assign a new name to the settings.
-            # And thus the new value is not accessible by other machines.
-            timeout = lib.mkOverride 5 "config.thing";
-          };
+          vendoredSettings = finalSettings;
         };
       };
   };
@@ -92,18 +88,6 @@ let
       roles.peer.tags.all = { };
     };
   };
-
-  filterInternals = lib.filterAttrs (n: _v: !lib.hasPrefix "_" n);
-
-  # Replace internal attributes ('_' prefix)
-  # So we catch their presence but don't check the value
-  mapInternalsRecursive = lib.mapAttrsRecursive (
-    path: v:
-    let
-      name = lib.last path;
-    in
-    if !lib.hasPrefix "_" name then v else name
-  );
 in
 {
   # settings should evaluate
@@ -117,10 +101,12 @@ in
       # instance = instance_foo
       # roles = peer
       # machines = jon
-      settings = filterInternals res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances.instance_foo.allMachines.jon.nixosModule.settings;
+      settings =
+        res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances.instance_foo.allMachines.jon.nixosModule.settings;
       machine =
         res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances.instance_foo.allMachines.jon.nixosModule.machine;
-      roles = mapInternalsRecursive res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances.instance_foo.allMachines.jon.nixosModule.roles;
+      roles =
+        res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances.instance_foo.allMachines.jon.nixosModule.roles;
     };
     expected = {
       instanceName = "instance_foo";
@@ -139,25 +125,21 @@ in
           machines = {
             jon = {
               settings = {
-                __functor = "__functor";
               };
             };
           };
           settings = {
-            __functor = "__functor";
           };
         };
         peer = {
           machines = {
             jon = {
               settings = {
-                __functor = "__functor";
                 timeout = "foo-peer-jon";
               };
             };
           };
           settings = {
-            __functor = "__functor";
             timeout = "foo-peer";
           };
         };
@@ -167,11 +149,9 @@ in
 
   test_per_instance_settings_vendoring = {
     expr =
-      mapInternalsRecursive
-        res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances."instance_foo".allMachines.jon.nixosModule.vendoredSettings;
+
+      res.importedModulesEvaluated.self-A.config.result.allRoles.peer.allInstances."instance_foo".allMachines.jon.nixosModule.vendoredSettings;
     expected = {
-      # Returns another override
-      __functor = "__functor";
       timeout = "config.thing";
     };
   };