diff --git a/nico.py b/nico.py
index 8c40543..4d1fa3c 100644
--- a/nico.py
+++ b/nico.py
@@ -139,12 +139,13 @@ def get_kiriban_list (
         for code in targets:
             if code in [kiriban[1]['contentId'] for kiriban in kiriban_list]:
                 continue
-            previous_views_count = cast (int, (VideoHistory
-                                               .where_has ('video',
-                                                   lambda q: q.where (
-                                                       'code', code))
-                                               .where ('fetched_at', '<', latest_fetched_at)
-                                               .max ('views_count')))
+            previous_views_count: int | None = (
+                    VideoHistory
+                    .where_has ('video', lambda q: q.where ('code', code))
+                    .where ('fetched_at', '<', latest_fetched_at)
+                    .max ('views_count'))
+            if previous_views_count is None:
+                previous_views_count = 0
             if previous_views_count >= kiriban_views_count:
                 continue
             video_info = get_video_info (code)