diff --git a/src/calibre/db/legacy.py b/src/calibre/db/legacy.py
index 384c75d71b..acab647f07 100644
--- a/src/calibre/db/legacy.py
+++ b/src/calibre/db/legacy.py
@@ -143,8 +143,8 @@ class LibraryDatabase(object):
         self.data.cache.initialize_template_cache()
 
     def all_ids(self):
-        for book_id in self.new_api.all_book_ids():
-            yield book_id
+        'All book ids in the db. This can no longer be a generator because of db locking.'
+        return tuple(self.new_api.all_book_ids())
 
     def is_empty(self):
         with self.new_api.read_lock: