diff --git a/sqlite_utils/cli.py b/sqlite_utils/cli.py
index 4cd728b..136411a 100644
--- a/sqlite_utils/cli.py
+++ b/sqlite_utils/cli.py
@@ -293,6 +293,7 @@ def views(
     \b
         sqlite-utils views trees.db
     """
+    assert tables.callback is not None
     tables.callback(
         path=path,
         fts4=False,