diff --git a/modules/di/src/binding.js b/modules/di/src/binding.js
index 986174dd4c..c98bbf03e3 100644
--- a/modules/di/src/binding.js
+++ b/modules/di/src/binding.js
@@ -50,7 +50,7 @@ export class BindingBuilder {
     );
   }
 
-  toFactory(factoryFunction:Function, {dependencies=null}={}):Binding {
+  toFactory(factoryFunction:Function, dependencies:List = null):Binding {
     return new Binding(
       Key.get(this.token),
       reflector.convertToFactory(factoryFunction),
@@ -59,7 +59,7 @@ export class BindingBuilder {
     );
   }
 
-  toAsyncFactory(factoryFunction:Function, {dependencies=null}={}):Binding {
+  toAsyncFactory(factoryFunction:Function, dependencies:List = null):Binding {
     return new Binding(
       Key.get(this.token),
       reflector.convertToFactory(factoryFunction),
diff --git a/modules/di/src/injector.js b/modules/di/src/injector.js
index 4698e92f86..09ff218c90 100644
--- a/modules/di/src/injector.js
+++ b/modules/di/src/injector.js
@@ -19,11 +19,11 @@ function _isWaiting(obj):bool {
 
 
 export class Injector {
-  constructor(bindings:List) {
+  constructor(bindings:List, parent:Injector = null) {
     var flatten = _flattenBindings(bindings, MapWrapper.create());
     this._bindings = this._createListOfBindings(flatten);
     this._instances = this._createInstances();
-    this._parent = null; //TODO: vsavkin make a parameter
+    this._parent = parent;
 
     this._asyncStrategy = new _AsyncInjectorStrategy(this);
     this._syncStrategy = new _SyncInjectorStrategy(this);
@@ -46,9 +46,7 @@ export class Injector {
   }
 
   createChild(bindings:List):Injector {
-    var inj = new Injector(bindings);
-    inj._parent = this; //TODO: vsavkin: change it when optional parameters are working
-    return inj;
+    return new Injector(bindings, this);
   }
 
 
diff --git a/modules/di/test/di/injector_spec.js b/modules/di/test/di/injector_spec.js
index da07617e55..0aec6acf57 100644
--- a/modules/di/test/di/injector_spec.js
+++ b/modules/di/test/di/injector_spec.js
@@ -125,7 +125,7 @@ export function main() {
     it('should support overriding factory dependencies', function () {
       var injector = new Injector([
         Engine,
-        bind(Car).toFactory((e) => new SportsCar(e), {dependencies: [Engine]})
+        bind(Car).toFactory((e) => new SportsCar(e), [Engine])
       ]);
 
       var car = injector.get(Car);