diff --git a/blueprints/tasks.py b/blueprints/tasks.py
index 116b3df..bbd76eb 100644
--- a/blueprints/tasks.py
+++ b/blueprints/tasks.py
@@ -284,7 +284,9 @@ def task_cache_actor() -> _Response:
         # )
 
         app.logger.info(f"actor cached for {iri}")
-        if activity.has_type([ap.ActivityType.CREATE, ap.ActivityType.ANNOUNCE]):
+        if activity.has_type(
+            [ap.ActivityType.CREATE, ap.ActivityType.ANNOUNCE]
+        ) and activity.get_object()._data.get("attachment", []):
             Tasks.cache_attachments(iri)
 
     except (ActivityGoneError, ActivityNotFoundError):
diff --git a/core/inbox.py b/core/inbox.py
index fc4b1f1..1d948c7 100644
--- a/core/inbox.py
+++ b/core/inbox.py
@@ -97,6 +97,9 @@ def _update_process_inbox(update: ap.Update, new_meta: _NewMeta) -> None:
             actor = ap.fetch_remote_activity(obj.get_actor().id)
         update_cached_actor(actor)
 
+    else:
+        raise ValueError(f"don't know how to update {obj!r}")
+
 
 @process_inbox.register
 def _create_process_inbox(create: ap.Create, new_meta: _NewMeta) -> None: