diff --git a/tests/topotests/conftest.py b/tests/topotests/conftest.py
index 7ad5d8c9ab..e00bebdaeb 100755
--- a/tests/topotests/conftest.py
+++ b/tests/topotests/conftest.py
@@ -61,6 +61,7 @@ def pytest_addoption(parser):
     parser.addoption(
         "--topology-only",
         action="store_true",
+        default=False,
         help="Only set up this topology, don't run tests",
     )