diff --git a/chrome/content/zotero/xpcom/sync/syncEventListeners.js b/chrome/content/zotero/xpcom/sync/syncEventListeners.js
index 694b95f70c..3d4f2a803f 100644
--- a/chrome/content/zotero/xpcom/sync/syncEventListeners.js
+++ b/chrome/content/zotero/xpcom/sync/syncEventListeners.js
@@ -208,7 +208,7 @@ Zotero.Sync.EventListeners.AutoSyncListener = {
 			autoSyncDelay || this._editTimeout,
 			false,
 			{
-				libraries: libraries.map(library => library.libraryID),
+				libraries: [...new Set(libraries.map(library => library.libraryID))],
 				fileLibraries: [...fileLibraries],
 				fullTextLibraries: [...fullTextLibraries]
 			}