diff --git a/tests/helpers/util.py b/tests/helpers/util.py
index faed6e1..c7c1bdf 100644
--- a/tests/helpers/util.py
+++ b/tests/helpers/util.py
@@ -7,5 +7,6 @@ def shim_argparse(testargv: list=[], tomldata: str=None):
     """
     ap = setup_argparse()
     args = ap.parse_args(testargv)
-    args = augment_args(args, tomldata)
+    if tomldata is not None:
+        args = augment_args(args, tomldata)
     return args
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