diff --git a/datasette/cli.py b/datasette/cli.py
index f3ea7d04..590d03f8 100644
--- a/datasette/cli.py
+++ b/datasette/cli.py
@@ -477,7 +477,7 @@ def uninstall(packages, yes):
     "--internal",
     type=click.Path(),
     help="Path to a persistent Datasette internal SQLite database",
-    envvar="DATASETTE_INTERNAL"
+    envvar="DATASETTE_INTERNAL",
 )
 def serve(
     files,