diff --git a/tests-unit/utils/extra_config_test.py b/tests-unit/utils/extra_config_test.py
index b23f5bd08..6d232079e 100644
--- a/tests-unit/utils/extra_config_test.py
+++ b/tests-unit/utils/extra_config_test.py
@@ -114,7 +114,7 @@ def test_load_extra_model_paths_expands_userpath(
     mock_yaml_safe_load.assert_called_once()
 
     # Check if open was called with the correct file path
-    mock_file.assert_called_once_with(dummy_yaml_file_name, 'r')
+    mock_file.assert_called_once_with(dummy_yaml_file_name, 'r', encoding='utf-8')
 
 
 @patch('builtins.open', new_callable=mock_open)