diff --git a/ann/src/main/python/dataflow/faiss_index_bq_dataset.py b/ann/src/main/python/dataflow/faiss_index_bq_dataset.py
index dd45070db..f0c1356d2 100644
--- a/ann/src/main/python/dataflow/faiss_index_bq_dataset.py
+++ b/ann/src/main/python/dataflow/faiss_index_bq_dataset.py
@@ -94,7 +94,9 @@ def parse_metric(config):
     raise Exception(f"Unknown metric: {metric_str}")
 
 
-def run_pipeline(argv=[]):
+def run_pipeline(argv=None):
+  if argv is None:
+    argv = []
   config = parse_d6w_config(argv)
   argv_with_extras = argv
   if config["gpu"]: