diff --git a/tests/quickshell/settings_write_sweep.py b/tests/quickshell/settings_write_sweep.py
index f8b396c..9cb9f79 100644
--- a/tests/quickshell/settings_write_sweep.py
+++ b/tests/quickshell/settings_write_sweep.py
@@ -178,6 +178,14 @@ def ipc(config_home: str, harness: str, *arguments: str) -> subprocess.Completed
 
 
 def main() -> int:
+    # Driven by settings-write-sweep-contract.sh, which starts the harness this
+    # needs and restores the desktop afterwards. Run bare -- by a suite runner
+    # walking the directory, say -- it says so instead of failing on argv.
+    if len(sys.argv) < 3:
+        print("settings_write_sweep is driven by tests/quickshell/"
+              "settings-write-sweep-contract.sh; run that instead.")
+        return 0
+
     config_home = sys.argv[1]
     harness = sys.argv[2]