diff --git a/tests/mock_vws/utils/__init__.py b/tests/mock_vws/utils/__init__.py
index c5decad57..08764a520 100644
--- a/tests/mock_vws/utils/__init__.py
+++ b/tests/mock_vws/utils/__init__.py
@@ -85,6 +85,7 @@ def auth_header_content_type(self) -> str:
 
 @beartype
 def make_image_file(
+    *,
     file_format: str,
     color_space: Literal["RGB", "CMYK"],
     width: int,