diff --git a/modules/angular2/src/alt_router/router.ts b/modules/angular2/src/alt_router/router.ts
index 65ea6ad595..cee4c1c72a 100644
--- a/modules/angular2/src/alt_router/router.ts
+++ b/modules/angular2/src/alt_router/router.ts
@@ -46,6 +46,7 @@ export class Router {
               private _componentResolver: ComponentResolver,
               private _urlSerializer: RouterUrlSerializer,
               private _routerOutletMap: RouterOutletMap, private _location: Location) {
+    this._prevTree = this._createInitialTree();
     this._setUpLocationChangeListener();
     this.navigateByUrl(this._location.path());
   }
@@ -62,6 +63,12 @@ export class Router {
 
   dispose(): void { ObservableWrapper.dispose(this._locationSubscription); }
 
+  private _createInitialTree(): RouteTree {
+    let root = new RouteSegment([new UrlSegment("", null, null)], null, DEFAULT_OUTLET_NAME,
+                                this._rootComponentType, null);
+    return new RouteTree(new TreeNode<RouteSegment>(root, []));
+  }
+
   private _setUpLocationChangeListener(): void {
     this._locationSubscription = this._location.subscribe(
         (change) => { this._navigate(this._urlSerializer.parse(change['url'])); });