diff --git a/lib/inventory/distributed-service/service-module.nix b/lib/inventory/distributed-service/service-module.nix
index 55000e89d..28c8d9434 100644
--- a/lib/inventory/distributed-service/service-module.nix
+++ b/lib/inventory/distributed-service/service-module.nix
@@ -216,7 +216,7 @@ in
 
                             options.extraModules = lib.mkOption {
                               default = [ ];
-                              type = types.listOf (types.either types.deferredModule types.str);
+                              type = types.listOf types.deferredModule;
                             };
                           }
                         )
diff --git a/modules/inventoryClass/role.nix b/modules/inventoryClass/role.nix
index 0f3a437f4..650cc56d1 100644
--- a/modules/inventoryClass/role.nix
+++ b/modules/inventoryClass/role.nix
@@ -73,15 +73,8 @@ in
             }
             ```
       '';
-      apply = value: if lib.isString value then value else builtins.seq (builtins.toJSON value) value;
       default = [ ];
-      type = types.listOf (
-        types.oneOf [
-          types.str
-          types.path
-          (types.attrsOf types.anything)
-        ]
-      );
+      type = types.listOf types.deferredModule;
     };
   };
 }
diff --git a/pkgs/clan-cli/clan_lib/services/modules_test.py b/pkgs/clan-cli/clan_lib/services/modules_test.py
index 0c3221f28..07e01b99b 100644
--- a/pkgs/clan-cli/clan_lib/services/modules_test.py
+++ b/pkgs/clan-cli/clan_lib/services/modules_test.py
@@ -316,3 +316,34 @@ def test_delete_static_service_instance(
 
     # TODO: improve error message
     assert "Cannot delete path 'instances.static" in str(excinfo.value)
+
+
+@pytest.mark.with_core
+def test_inline_extra_modules(clan_flake: Callable[..., Flake]) -> None:
+    """ExtraModules are excluded from serialization to allow arbitrary inlining"""
+    # Data that can be mutated via API calls
+    mutable_inventory_json: Inventory = {
+        "instances": {
+            "static": {"module": {"name": "admin"}},
+        }
+    }
+    nix = r"""
+    {
+        inventory.instances.static = {
+            roles.default.extraModules = [
+                (_: { }) # non-serializable inline module
+            ];
+        };
+    }
+    """
+
+    flake = clan_flake(
+        {},
+        raw=nix,
+        mutable_inventory_json=mutable_inventory_json,
+    )
+
+    # Ensure preconditions
+    instances = list_service_instances(flake)
+
+    assert set(instances.keys()) == {"static"}