diff --git a/content/treestyletab/bookmarksOverlay.js b/content/treestyletab/bookmarksOverlay.js
index 430d683b..a456a3b8 100644
--- a/content/treestyletab/bookmarksOverlay.js
+++ b/content/treestyletab/bookmarksOverlay.js
@@ -111,7 +111,7 @@ var TreeStyleTabBookmarksService = {
 		var treeStructure = aIDs.map(function(aId, aIndex) {
 				let id = this.getParentItem(aId);
 				let index = aIDs.indexOf(id);
-				return index >= aIndex ? aDefaultParentID : index ;
+				return index > aIndex || index < -1 ? aDefaultParentID : index ;
 			}, this);
 
 		/* Correct patterns like: