diff --git a/lib/model-builder.js b/lib/model-builder.js
index c27300bd..bdb842cb 100644
--- a/lib/model-builder.js
+++ b/lib/model-builder.js
@@ -217,18 +217,30 @@ ModelBuilder.prototype.define = function defineClass(className, properties, sett
 
         subclassProperties = subclassProperties || {};
         subclassSettings = subclassSettings || {};
-        
+
+        // Check if subclass redefines the ids
+        var idFound = false;
+        for(var k in subclassProperties) {
+            if(subclassProperties[k].id) {
+                idFound = true;
+                break;
+            }
+        }
+
         // Merging the properties
         Object.keys(properties).forEach(function (key) {
-          // don't inherit the id property
-          if(key !== 'id' && typeof subclassProperties[key] === 'undefined') {
+          if(idFound && properties[key].id) {
+              // don't inherit id properties
+              return;
+          }
+          if(subclassProperties[key] === undefined) {
             subclassProperties[key] = properties[key];
           }
         });
 
         // Merge the settings
         Object.keys(settings).forEach(function (key) {
-          if(typeof subclassSettings[key] === 'undefined') {
+          if(subclassSettings[key] === undefined) {
             subclassSettings[key] = settings[key];
           }
         });
@@ -376,7 +388,6 @@ ModelBuilder.prototype.extendModel = function (model, props) {
         var definition = props[propName];
         t.defineProperty(model, propName, definition);
     });
-    t.definitions[model].build(true);
 };
 
 
diff --git a/test/loopback-dl.test.js b/test/loopback-dl.test.js
index e095a0cb..c884e9d3 100644
--- a/test/loopback-dl.test.js
+++ b/test/loopback-dl.test.js
@@ -429,5 +429,40 @@ describe('Load models from json', function () {
             assert(new m());
         }
     });
+
+    it('should be able to extend models', function (done) {
+        var modelBuilder = new ModelBuilder();
+
+        var User = modelBuilder.define('User', {
+            name: String,
+            bio: ModelBuilder.Text,
+            approved: Boolean,
+            joinedAt: Date,
+            age: Number
+        });
+
+        var Customer = User.extend('Customer', {customerId: {type: String, id: true}});
+
+        var customer = new Customer({name: 'Joe', age: 20, customerId: 'c01'});
+
+        customer.should.be.a('object').and.have.property('name', 'Joe');
+        customer.should.have.property('name', 'Joe');
+        customer.should.have.property('age', 20);
+        customer.should.have.property('customerId', 'c01');
+        customer.should.not.have.property('bio');
+
+        // The properties are defined at prototype level
+        assert.equal(Object.keys(customer).length, 0);
+        var count = 0;
+        for(var p in customer) {
+            if(typeof customer[p] !== 'function') {
+                count++;
+            }
+        }
+        assert.equal(count, 7); // Please note there is an injected id from User prototype
+        assert.equal(Object.keys(customer.toObject()).length, 6);
+
+        done(null, customer);
+    });
 });