diff --git a/chrome/content/zotero/xpcom/data/dataObjects.js b/chrome/content/zotero/xpcom/data/dataObjects.js
index 147e9d73a..4a0f75f44 100644
--- a/chrome/content/zotero/xpcom/data/dataObjects.js
+++ b/chrome/content/zotero/xpcom/data/dataObjects.js
@@ -530,6 +530,8 @@ Zotero.DataObjects.prototype._diffCreators = function (data1, data2) {
 }
 
 Zotero.DataObjects.prototype._diffCollections = function (data1, data2) {
+	// Child items shouldn't have collections properties, but just in case one does
+	if (!data2) return false;
 	if (data1.length != data2.length) return false;
 	let c1 = data1.concat();
 	let c2 = data2.concat();
diff --git a/chrome/content/zotero/xpcom/data/item.js b/chrome/content/zotero/xpcom/data/item.js
index 2b8c4a216..648cb3b0a 100644
--- a/chrome/content/zotero/xpcom/data/item.js
+++ b/chrome/content/zotero/xpcom/data/item.js
@@ -4216,10 +4216,12 @@ Zotero.Item.prototype.toJSON = Zotero.Promise.coroutine(function* (options) {
 	}
 	
 	// Collections
-	yield this.loadCollections();
-	obj.collections = this.getCollections().map(function (id) {
-		return this.ContainerObjectsClass.getLibraryAndKeyFromID(id).key;
-	}.bind(this));
+	if (this.isTopLevelItem()) {
+		yield this.loadCollections();
+		obj.collections = this.getCollections().map(function (id) {
+			return this.ContainerObjectsClass.getLibraryAndKeyFromID(id).key;
+		}.bind(this));
+	}
 	
 	// Relations
 	yield this.loadRelations();