diff --git a/src/calibre/srv/library_broker.py b/src/calibre/srv/library_broker.py
index 1e5681d7a6..1a76671227 100644
--- a/src/calibre/srv/library_broker.py
+++ b/src/calibre/srv/library_broker.py
@@ -246,9 +246,10 @@ class GuiLibraryBroker(LibraryBroker):
         for library_id in tuple(self.loaded_dbs):
             if library_id != self.gui_library_id and now - self.last_used_times[
                 library_id] > EXPIRED_AGE:
-                db = self.loaded_dbs.pop(library_id)
-                db.close()
-                db.break_cycles()
+                db = self.loaded_dbs.pop(library_id, None)
+                if db is not None:
+                    db.close()
+                    db.break_cycles()
 
     def prune_loaded_dbs(self):
         with self: