diff --git a/divent/bot.py b/divent/bot.py
index 34571ba..90fc49b 100644
--- a/divent/bot.py
+++ b/divent/bot.py
@@ -221,7 +221,10 @@ async def subscribe(entity_id: str):
             entity_id=guild.vanity_url_code or guild.id,
         )
 
-    user = await client.get_or_fetch_user(int(entity_id))
+    try:
+        user = await client.get_or_fetch_user(int(entity_id))
+    except ValueError:
+        return redirect(url_for(".login"))
 
     if user and str(user.id) == entity_id:
         return await render_template(
@@ -281,7 +284,10 @@ async def ical(entity_id: str):
 
         return calendar.serialize()
 
-    user = await client.get_or_fetch_user(int(entity_id))
+    try:
+        user = await client.get_or_fetch_user(int(entity_id))
+    except ValueError:
+        return redirect(url_for(".login"))
 
     if user:
         calendar = Calendar()