diff --git a/packages/client-sync/src/local-sync-worker/sync-tasks/fetch-new-messages-in-folder.imap.es6 b/packages/client-sync/src/local-sync-worker/sync-tasks/fetch-new-messages-in-folder.imap.es6
index 9492e2638..c3585b00f 100644
--- a/packages/client-sync/src/local-sync-worker/sync-tasks/fetch-new-messages-in-folder.imap.es6
+++ b/packages/client-sync/src/local-sync-worker/sync-tasks/fetch-new-messages-in-folder.imap.es6
@@ -17,6 +17,9 @@ class FetchNewMessagesInFolderIMAP extends FetchMessagesInFolderIMAP {
     this._logger.log(`🔜 📂 🆕  ${this._folder.name} - Looking for new messages`)
     this._db = db;
     this._imap = imap;
+    if (!syncWorker) {
+      throw new Error(`SyncWorker not passed to runTask`);
+    }
     this._syncWorker = syncWorker;
     const {syncState: {fetchedmax}} = this._folder