diff --git a/test/test_job_config.py b/test/test_job_config.py
index ccdaf206..0e3d9c63 100644
--- a/test/test_job_config.py
+++ b/test/test_job_config.py
@@ -9,12 +9,12 @@ class TestJobConfig:
     def test_command_line_args(self):
         config = JobConfig()
         config.parse_args([])
-        assert config.model.name == "llama"
+        assert config.training.steps == -1
 
     def test_job_config_file(self):
         config = JobConfig()
         config.parse_args(["--job.config_file", "./train_configs/debug_model.toml"])
-        assert config.model.name == "llama"
+        assert config.training.steps == 10
 
     def test_job_file_does_not_exist(self):
         with pytest.raises(FileNotFoundError):
diff --git a/torchtrain/config_manager.py b/torchtrain/config_manager.py
index ff8afe8f..613f9411 100644
--- a/torchtrain/config_manager.py
+++ b/torchtrain/config_manager.py
@@ -1,3 +1,6 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# This software may be used and distributed according to the terms of the Llama 2 Community License Agreement.
+
 # Copyright (c) Meta Platforms, Inc. and affiliates.
 # All rights reserved.
 import argparse
@@ -17,16 +20,16 @@ class JobConfig:
     Semantics:
     - Default config is loaded from a toml file. If no toml file is provided,
     then the default config is loaded from argparse defaults.
+    - if toml file has missing keys, they are filled with argparse defaults.
     """
 
     def parse_args(self, args_list: list = sys.argv[1:]):
         args = JobConfig.init_args_from_command_line(args_list)
         config_file = getattr(args, "job.config_file", None)
-        if config_file is None:
-            args_dict = self._args_to_two_level_dict(args)
-        else:
+        args_dict = self._args_to_two_level_dict(args)
+        if config_file is not None:
             with open(config_file, "rb") as f:
-                args_dict = tomllib.load(f)
+                args_dict |= tomllib.load(f)
         for k, v in args_dict.items():
             class_type = type(k.title(), (), v)
             setattr(self, k, class_type())