diff --git a/lib/Instance.js b/lib/Instance.js
index c7b4748..3cb525a 100644
--- a/lib/Instance.js
+++ b/lib/Instance.js
@@ -70,10 +70,10 @@ function Instance(collection, doc, options, isNew) {
 		if (targetProperty === '_id' || targetProperty === "id") continue;
 
 		(function (sourceProperty) {
-			if (k === '_id')
+			if (sourceProperty === '_id' || sourceProperty === 'id')
 				Object.defineProperty($, targetProperty, {
 					get: function () {
-						return newDoc[sourceProperty];
+						return newDoc['_id'];
 					},
 					enumerable: true
 				});
@@ -100,8 +100,10 @@ function Instance(collection, doc, options, isNew) {
 	}
 
 	for (k in options.methods) {
+		if (k === '_id' || k === "id") continue;
+		
 		(function (sourceProperty) {
-			Object.defineProperty($, k, {
+			Object.defineProperty($, sourceProperty, {
 				value: function () {
 					return options.methods[sourceProperty].apply($, arguments);
 				}
@@ -110,8 +112,10 @@ function Instance(collection, doc, options, isNew) {
 	}
 
 	for (k in options.virtuals) {
+		if (k === '_id' || k === "id") continue;
+
 		(function (sourceProperty) {
-			Object.defineProperty($, k, {
+			Object.defineProperty($, sourceProperty, {
 				get: function () {
 					return options.virtuals[sourceProperty].call($);
 				}
@@ -211,8 +215,13 @@ function Instance(collection, doc, options, isNew) {
 
 	Object.defineProperty($, 'update', {
 		value: function (callback) {
+			/// <signature>
+			/// <summary>Updates this object from the database, bringing it up to date</summary>
+			/// </signature>
+			/// <signature>
 			/// <summary>Updates this object from the database, bringing it up to date</summary>
 			/// <param name="callback" type="Function">A function to be called once the update is complete</param>
+			/// </signature>
 
 			var conditions = { _id: $.id };
 
@@ -224,7 +233,8 @@ function Instance(collection, doc, options, isNew) {
 				transform.down(options.transforms, updated);
 
 				oldDoc = newDoc = updated;
-				return callback(null, $);
+
+				if(callback) return callback(null, $);
 			});
 		}
 	});
diff --git a/lib/Model.js b/lib/Model.js
index 56d3f51..4e42946 100644
--- a/lib/Model.js
+++ b/lib/Model.js
@@ -227,12 +227,14 @@ Model.prototype.remove = function (conditions, callback) {
 	this.collection.remove(conditions, { w: callback ? 1 : 0 }, callback);
 };
 
-Model.prototype.aggregate = function (chain, callback) {
+Model.prototype.aggregate = function () {
+	/// <signature>
 	/// <summary>Allows you to execute aggregation queries using MongoDB's aggregation framework</summary>
 	/// <param name="chain" type="Array" elementType="Object">The aggregation toolchain to run</param>
 	/// <param name="callback" type="Function">A function to be called once aggregation has been completed</param>
-
-	this.collection.aggregate(chain, callback);
+	/// </signature>
+	
+	this.collection.aggregate.apply(this.collection, arguments);
 };
 
 Model.prototype.ensureIndex = function (spec, options, callback) {