diff --git a/lib/Instance.js b/lib/Instance.js
index 22200b4..7051d5d 100644
--- a/lib/Instance.js
+++ b/lib/Instance.js
@@ -158,9 +158,7 @@ function Instance(model, doc, isNew) {
 			if (!!isNew || Object.keys(changes).length > 0) {
 				var runOptions = function () {
 					
-					var conditions = { _id: $.id };
-
-					model.toSource(conditions);
+					var conditions = model.uniqueConditions(newDoc);
 
 					model.collection.update(conditions, changes, { w: 1 }, function (err, updateCount) {
 						if (err) return cb(err);
@@ -171,8 +169,8 @@ function Instance(model, doc, isNew) {
 								
 								model.fromSource(updated);
 
-								newDoc = _.clone(updated);
-								oldDoc = _.clone(updated);
+								newDoc = _.cloneDeep(updated);
+								oldDoc = _.cloneDeep(updated);
 
 								addSchemaProperties();
 
@@ -204,9 +202,7 @@ function Instance(model, doc, isNew) {
 			/// <param name="callback" type="Function">A function to be called once the update is complete</param>
 			/// </signature>
 
-			var conditions = { _id: $.id };
-
-			model.toSource(conditions);
+			var conditions = model.uniqueConditions(oldDoc);
 
 			model.collection.findOne(conditions, function (err, updated) {
 				if (err) return cb(err);
@@ -227,10 +223,8 @@ function Instance(model, doc, isNew) {
 			/// <summary>Removes this object from the database collection</summary>
 			/// <param name="callback" type="Function">A function to be called when the object has been removed</param>
 
-			if (oldDoc._id) {
-				var conditions = { _id: $.id };
-
-				model.toSource(conditions);
+			if (!isNew) {
+				var conditions = model.uniqueConditions(newDoc);
 
 				model.collection.remove(conditions, callback);
 			} else {
diff --git a/lib/Model.js b/lib/Model.js
index c023600..d380426 100644
--- a/lib/Model.js
+++ b/lib/Model.js
@@ -100,6 +100,20 @@ Model.prototype.toSource = function(document) {
 	this.preprocessors.reverse(document);
 };
 
+Model.prototype.uniqueConditions = function(document) {
+	/// <summary>Gets a set of MongoDB conditions which uniquely identify the given document for this model in source form/summary>
+	/// <param name="document" type="Object">The document to find the unique conditions for</param>
+	/// <returns type="Object"/>
+
+	var testDoc = _.cloneDeep(document);
+	this.toSource(testDoc);
+
+	var conditions = {
+		_id: testDoc[_id]
+	};
+	return conditions;
+};
+
 Model.prototype.wrap = function (document, isNew) {
 	/// <signature>
 	/// <summary>Wraps the given database object in this model's Instance wrapper</summary>