diff --git a/src/openjd/adaptor_runtime/_entrypoint.py b/src/openjd/adaptor_runtime/_entrypoint.py
index 86a6aae..5275ccf 100644
--- a/src/openjd/adaptor_runtime/_entrypoint.py
+++ b/src/openjd/adaptor_runtime/_entrypoint.py
@@ -241,6 +241,7 @@ def _build_argparser(self) -> ArgumentParser:
         path_mapping_rules = ArgumentParser(add_help=False)
         path_mapping_rules.add_argument(
             "--path-mapping-rules",
+            default="",
             required=False,
             type=_load_data,
             help=_CLI_HELP_TEXT["path_mapping_rules"],
diff --git a/test/openjd/adaptor_runtime/unit/background/test_frontend_runner.py b/test/openjd/adaptor_runtime/unit/background/test_frontend_runner.py
index 114e586..f454899 100644
--- a/test/openjd/adaptor_runtime/unit/background/test_frontend_runner.py
+++ b/test/openjd/adaptor_runtime/unit/background/test_frontend_runner.py
@@ -80,10 +80,11 @@ def test_initializes_backend_process(
             adaptor_module.__package__ = "package"
             conn_file_path = "/path"
             init_data = {"init": "data"}
+            path_mapping_data = {}
             runner = FrontendRunner(conn_file_path)
 
             # WHEN
-            runner.init(adaptor_module, init_data)
+            runner.init(adaptor_module, init_data, path_mapping_data)
 
             # THEN
             assert caplog.messages == [
@@ -104,6 +105,8 @@ def test_initializes_backend_process(
                     conn_file_path,
                     "--init-data",
                     json.dumps(init_data),
+                    "--path-mapping-rules",
+                    json.dumps(path_mapping_data),
                 ],
                 shell=False,
                 close_fds=True,
diff --git a/test/openjd/adaptor_runtime/unit/test_entrypoint.py b/test/openjd/adaptor_runtime/unit/test_entrypoint.py
index 3747676..4b638b0 100644
--- a/test/openjd/adaptor_runtime/unit/test_entrypoint.py
+++ b/test/openjd/adaptor_runtime/unit/test_entrypoint.py
@@ -415,7 +415,7 @@ def test_runs_background_start(
 
         # THEN
         _parse_args_mock.assert_called_once()
-        mock_magic_init.assert_called_once_with(mock_adaptor_module, {})
+        mock_magic_init.assert_called_once_with(mock_adaptor_module, {}, {})
         mock_magic_start.assert_called_once_with(conn_file)
         mock_start.assert_called_once_with()