diff --git a/backbone.js b/backbone.js
index 0bf20516..edca0905 100644
--- a/backbone.js
+++ b/backbone.js
@@ -734,7 +734,9 @@
     // Get a model from the set by id.
     get: function(obj) {
       if (obj == null) return void 0;
-      return this._byId[obj.id != null ? obj.id : obj] || this._byCid[obj.cid || obj];
+      var idAttr = this.model.prototype.idAttribute;
+      return this._byId[obj[idAttr] != null ? obj[idAttr] : obj.id != null ? obj.id : obj]
+             || this._byCid[obj.cid || obj];
     },
 
     // Get the model at the given index.
@@ -781,7 +783,6 @@
     update: function(models, options) {
       var model, i, l, existing;
       var add = [], remove = [], modelMap = {};
-      var idAttr = this.model.prototype.idAttribute;
       options = _.extend({add: true, merge: true, remove: true}, options);
       if (options.parse) models = this.parse(models, options);
 
@@ -794,7 +795,7 @@
       // Determine which models to add and merge, and which to remove.
       for (i = 0, l = models.length; i < l; i++) {
         model = models[i];
-        existing = this.get(model.id || model.cid || model[idAttr]);
+        existing = this.get(model);
         if (options.remove && existing) modelMap[existing.cid] = true;
         if ((options.add && !existing) || (options.merge && existing)) {
           add.push(model);
diff --git a/test/collection.js b/test/collection.js
index 4c79e290..9ac954ed 100644
--- a/test/collection.js
+++ b/test/collection.js
@@ -62,13 +62,15 @@ $(document).ready(function() {
     strictEqual(collection.last().get('a'), 4);
   });
 
-  test("get", 3, function() {
+  test("get", 5, function() {
     equal(col.get(0), d);
     equal(col.get(2), b);
+    equal(col.get({id: 1}), c);
+    equal(col.get(c.clone()), c);
     equal(col.get(col.first().cid), col.first());
   });
 
-  test("get with non-default ids", 2, function() {
+  test("get with non-default ids", 4, function() {
     var col = new Backbone.Collection();
     var MongoModel = Backbone.Model.extend({
       idAttribute: '_id'
@@ -78,6 +80,12 @@ $(document).ready(function() {
     equal(col.get(100), model);
     model.set({_id: 101});
     equal(col.get(101), model);
+
+    var Col2 = Backbone.Collection.extend({ model: MongoModel });
+    col2 = new Col2();
+    col2.push(model);
+    equal(col2.get({_id: 101}), model);
+    equal(col2.get(model.clone()), model);
   });
 
   test("update index when id changes", 3, function() {