diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index 217f2a9dc..08d67df30 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -2428,7 +2428,8 @@ Zotero.ItemTreeView.prototype.onColumnPickerShowing = function (event) {
 		moreMenuPopup.setAttribute('anonid', id + '-popup');
 		
 		let treecols = menupopup.parentNode.parentNode;
-		let subs = treecols.getElementsByAttribute('submenu', 'true').map(x => x.getAttribute('label'));
+		let subs = Array.from(treecols.getElementsByAttribute('submenu', 'true'))
+			.map(x => x.getAttribute('label'));
 		
 		var moreItems = [];