diff --git a/stix2/test/v21/test_datastore_relational_db.py b/stix2/test/v21/test_datastore_relational_db.py
index 0a8751b4..c9a774f3 100644
--- a/stix2/test/v21/test_datastore_relational_db.py
+++ b/stix2/test/v21/test_datastore_relational_db.py
@@ -6,7 +6,7 @@
 import stix2.properties
 
 store = RelationalDBStore(
-    f"postgresql://{os.environ['POSTGRES_USER']}:{os.environ['POSTGRES_PASSWORD']}@0.0.0.0:5432/postgres",
+    f"postgresql://{os.getenv('POSTGRES_USER', 'postgres')}:{os.getenv('POSTGRES_PASSWORD', 'postgres')}@0.0.0.0:5432/postgres",
     True,
     None,
     False,