diff --git a/watson/management/commands/buildwatson.py b/watson/management/commands/buildwatson.py
index 50d5c76..446e2ae 100644
--- a/watson/management/commands/buildwatson.py
+++ b/watson/management/commands/buildwatson.py
@@ -88,7 +88,7 @@ class Command(BaseCommand):
             model registration. WARNING: buildwatson must be rerun if the filter \
             changes or the index will be incomplete."
         )
-        parser.add_argument
+        parser.add_argument(
             '--batch_size',
             action='store',
             default=100,