diff --git a/chrome/content/zotero/xpcom/data/item.js b/chrome/content/zotero/xpcom/data/item.js
index 226292171e..4b0d4e5c80 100644
--- a/chrome/content/zotero/xpcom/data/item.js
+++ b/chrome/content/zotero/xpcom/data/item.js
@@ -1382,7 +1382,7 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 		}
 	}
 	
-	// Parent item
+	// Parent item (DB update is done below after collection removals)
 	var parentItemKey = this.parentKey;
 	var parentItemID = this.ObjectsClass.getIDFromLibraryAndKey(this.libraryID, parentItemKey) || null;
 	if (this._changed.parentKey) {
@@ -1411,9 +1411,6 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 			}
 		}
 		else {
-			let type = Zotero.ItemTypes.getName(itemTypeID);
-			let Type = type[0].toUpperCase() + type.substr(1);
-			
 			if (parentItemKey) {
 				if (!parentItemID) {
 					// TODO: clear caches
@@ -1494,15 +1491,6 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 				}
 			}
 			
-			// Update DB, if not a note or attachment we're changing below
-			if (!this._changed.attachmentData &&
-					(!this._changed.note || !this.isNote())) {
-				let sql = "UPDATE item" + Type + "s SET parentItemID=? "
-							+ "WHERE itemID=?";
-				let bindParams = [parentItemID, this.id];
-				yield Zotero.DB.queryAsync(sql, bindParams);
-			}
-			
 			// Update the counts of the previous and new sources
 			if (oldParentItemID) {
 				reloadParentChildItems[oldParentItemID] = true;
@@ -1579,6 +1567,67 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 		yield Zotero.DB.queryAsync(sql, itemID);
 	}
 	
+	// Collections
+	//
+	// Only diffing and removal are done here. Additions have to be done below after parentItemID has
+	// been updated in itemAttachments/itemNotes, since a child item that was made a standalone item and
+	// added to a collection can't be added to the collection while it still has a parent, and vice
+	// versa, due to the trigger checks on collectionItems/itemAttachments/itemNotes.
+	if (this._changed.collections) {
+		if (libraryType == 'publications') {
+			throw new Error("Items in My Publications cannot be added to collections");
+		}
+		
+		let oldCollections = this._previousData.collections || [];
+		let newCollections = this._collections;
+		
+		let toAdd = Zotero.Utilities.arrayDiff(newCollections, oldCollections);
+		let toRemove = Zotero.Utilities.arrayDiff(oldCollections, newCollections);
+		
+		env.collectionsAdded = toAdd;
+		env.collectionsRemoved = toRemove;
+		
+		if (toRemove.length) {
+			let sql = "DELETE FROM collectionItems WHERE itemID=? AND collectionID IN ("
+				+ toRemove.join(',')
+				+ ")";
+			yield Zotero.DB.queryAsync(sql, this.id);
+			
+			for (let i=0; i<toRemove.length; i++) {
+				let collectionID = toRemove[i];
+				
+				if (!env.options.skipNotifier) {
+					Zotero.Notifier.queue(
+						'remove',
+						'collection-item',
+						collectionID + '-' + this.id,
+						{},
+						env.options.notifierQueue
+					);
+				}
+			}
+			
+			// Remove this item from any loaded collections' cached item lists after commit
+			Zotero.DB.addCurrentCallback("commit", function () {
+				for (let i = 0; i < toRemove.length; i++) {
+					this.ContainerObjectsClass.unregisterChildItem(toRemove[i], this.id);
+				}
+			}.bind(this));
+		}
+	}
+	
+	// Add parent item for existing item, if note or attachment data isn't going to be updated below
+	//
+	// Technically this doesn't have to go below collection removals, but only because the
+	// 'collectionitem must be top level' trigger check applies only to INSERTs, not UPDATEs, which was
+	// probably done in an earlier attempt to solve this problem.
+	if (!isNew && this._changed.parentKey && !this._changed.note && !this._changed.attachmentData) {
+		let type = Zotero.ItemTypes.getName(itemTypeID);
+		let Type = type[0].toUpperCase() + type.substr(1);
+		let sql = "UPDATE item" + Type + "s SET parentItemID=? WHERE itemID=?";
+		yield Zotero.DB.queryAsync(sql, [parentItemID, this.id]);
+	}
+	
 	// Note
 	if ((isNew && this.isNote()) || this._changed.note) {
 		if (!isNew) {
@@ -1627,7 +1676,6 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 			reloadParentChildItems[parentItemID] = true;
 		}
 	}
-	
 	if (this._changed.attachmentData) {
 		let sql = "REPLACE INTO itemAttachments "
 			+ "(itemID, parentItemID, linkMode, contentType, charsetID, path, "
@@ -1666,6 +1714,39 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 		}
 	}
 	
+	// Add to new collections
+	if (env.collectionsAdded) {
+		let toAdd = env.collectionsAdded;
+		for (let i=0; i<toAdd.length; i++) {
+			let collectionID = toAdd[i];
+			
+			let sql = "SELECT IFNULL(MAX(orderIndex)+1, 0) FROM collectionItems "
+				+ "WHERE collectionID=?";
+			let orderIndex = yield Zotero.DB.valueQueryAsync(sql, collectionID);
+			
+			sql = "INSERT OR IGNORE INTO collectionItems "
+				+ "(collectionID, itemID, orderIndex) VALUES (?, ?, ?)";
+			yield Zotero.DB.queryAsync(sql, [collectionID, this.id, orderIndex]);
+			
+			if (!env.options.skipNotifier) {
+				Zotero.Notifier.queue(
+					'add',
+					'collection-item',
+					collectionID + '-' + this.id,
+					{},
+					env.options.notifierQueue
+				);
+			}
+		}
+		
+		// Add this item to any loaded collections' cached item lists after commit
+		Zotero.DB.addCurrentCallback("commit", function () {
+			for (let i = 0; i < toAdd.length; i++) {
+				this.ContainerObjectsClass.registerChildItem(toAdd[i], this.id);
+			}
+		}.bind(this));
+	}
+	
 	// Tags
 	if (this._changed.tags) {
 		let oldTags = this._previousData.tags || [];
@@ -1720,81 +1801,6 @@ Zotero.Item.prototype._saveData = Zotero.Promise.coroutine(function* (env) {
 		}
 	}
 	
-	// Collections
-	if (this._changed.collections) {
-		if (libraryType == 'publications') {
-			throw new Error("Items in My Publications cannot be added to collections");
-		}
-		
-		let oldCollections = this._previousData.collections || [];
-		let newCollections = this._collections;
-		
-		let toAdd = Zotero.Utilities.arrayDiff(newCollections, oldCollections);
-		let toRemove = Zotero.Utilities.arrayDiff(oldCollections, newCollections);
-
-		env.collectionsAdded = toAdd;
-		env.collectionsRemoved = toRemove;
-		
-		if (toAdd.length) {
-			for (let i=0; i<toAdd.length; i++) {
-				let collectionID = toAdd[i];
-				
-				let sql = "SELECT IFNULL(MAX(orderIndex)+1, 0) FROM collectionItems "
-					+ "WHERE collectionID=?";
-				let orderIndex = yield Zotero.DB.valueQueryAsync(sql, collectionID);
-				
-				sql = "INSERT OR IGNORE INTO collectionItems "
-					+ "(collectionID, itemID, orderIndex) VALUES (?, ?, ?)";
-				yield Zotero.DB.queryAsync(sql, [collectionID, this.id, orderIndex]);
-				
-				if (!env.options.skipNotifier) {
-					Zotero.Notifier.queue(
-						'add',
-						'collection-item',
-						collectionID + '-' + this.id,
-						{},
-						env.options.notifierQueue
-					);
-				}
-			}
-			
-			// Add this item to any loaded collections' cached item lists after commit
-			Zotero.DB.addCurrentCallback("commit", function () {
-				for (let i = 0; i < toAdd.length; i++) {
-					this.ContainerObjectsClass.registerChildItem(toAdd[i], this.id);
-				}
-			}.bind(this));
-		}
-		
-		if (toRemove.length) {
-			let sql = "DELETE FROM collectionItems WHERE itemID=? AND collectionID IN ("
-				+ toRemove.join(',')
-				+ ")";
-			yield Zotero.DB.queryAsync(sql, this.id);
-			
-			for (let i=0; i<toRemove.length; i++) {
-				let collectionID = toRemove[i];
-				
-				if (!env.options.skipNotifier) {
-					Zotero.Notifier.queue(
-						'remove',
-						'collection-item',
-						collectionID + '-' + this.id,
-						{},
-						env.options.notifierQueue
-					);
-				}
-			}
-			
-			// Remove this item from any loaded collections' cached item lists after commit
-			Zotero.DB.addCurrentCallback("commit", function () {
-				for (let i = 0; i < toRemove.length; i++) {
-					this.ContainerObjectsClass.unregisterChildItem(toRemove[i], this.id);
-				}
-			}.bind(this));
-		}
-	}
-	
 	// Update child item counts and contents
 	if (reloadParentChildItems) {
 		for (let parentItemID in reloadParentChildItems) {
@@ -4157,10 +4163,6 @@ Zotero.Item.prototype.fromJSON = function (json) {
 			this.setTags(json.tags);
 			break;
 		
-		case 'collections':
-			this.setCollections(json.collections);
-			break;
-		
 		case 'relations':
 			this.setRelations(json.relations);
 			break;
@@ -4220,6 +4222,10 @@ Zotero.Item.prototype.fromJSON = function (json) {
 		}
 	}
 	
+	if (json.collections || this._collections.length) {
+		this.setCollections(json.collections);
+	}
+	
 	// Clear existing fields not specified
 	var previousFields = this.getUsedFields(true);
 	for (let field of previousFields) {
diff --git a/test/tests/itemTest.js b/test/tests/itemTest.js
index 9bbb2bf73e..508465e421 100644
--- a/test/tests/itemTest.js
+++ b/test/tests/itemTest.js
@@ -1448,6 +1448,22 @@ describe("Zotero.Item", function () {
 			assert.strictEqual(item.getField('accessDate'), '');
 		});
 		
+		it("should remove child item from collection if 'collections' property not provided", function* () {
+			var collection = yield createDataObject('collection');
+			// Create standalone attachment in collection
+			var attachment = yield importFileAttachment('test.png', { collections: [collection.id] });
+			var item = yield createDataObject('item', { collections: [collection.id] });
+			
+			var json = attachment.toJSON();
+			json.path = 'storage:test2.png';
+			// Add to parent, which implicitly removes from collection
+			json.parentItem = item.key;
+			delete json.collections;
+			Zotero.debug(json);
+			attachment.fromJSON(json);
+			yield attachment.save();
+		});
+		
 		it("should ignore unknown fields", function* () {
 			var json = {
 				itemType: "journalArticle",