diff --git a/knockout/knockout.d.ts b/knockout/knockout.d.ts
index 9c581cd27..9b86be44d 100644
--- a/knockout/knockout.d.ts
+++ b/knockout/knockout.d.ts
@@ -548,7 +548,7 @@ interface KnockoutStatic {
 interface KnockoutBindingProvider {
 	nodeHasBindings(node: Node): boolean;
 	getBindings(node: Node, bindingContext: KnockoutBindingContext): {};
-	getBindingAccessors(node: Node, bindingContext: KnockoutBindingContext): { [key: string]: string; };
+	getBindingAccessors?(node: Node, bindingContext: KnockoutBindingContext): { [key: string]: string; };
 }
 
 interface KnockoutComponents {
diff --git a/knockout/tests/knockout-templatingBehaviors-tests.ts b/knockout/tests/knockout-templatingBehaviors-tests.ts
index 7be02d4cd..50ec27572 100644
--- a/knockout/tests/knockout-templatingBehaviors-tests.ts
+++ b/knockout/tests/knockout-templatingBehaviors-tests.ts
@@ -363,11 +363,11 @@ describe('Templating', function() {
         // and external (non-rewritten) ones
         var originalBindingProvider = ko.bindingProvider.instance;
         ko.bindingProvider.instance = {
-            nodeHasBindings: function(node, bindingContext) {
-                return (node.tagName == 'EM') || originalBindingProvider.nodeHasBindings(node, bindingContext);
+            nodeHasBindings: function(node) {
+                return ((<Element>node).tagName == 'EM') || originalBindingProvider.nodeHasBindings(node);
             },
             getBindings: function(node, bindingContext) {
-                if (node.tagName == 'EM')
+                if ((<Element>node).tagName == 'EM')
                     return { text: ++model.numBindings };
                 return originalBindingProvider.getBindings(node, bindingContext);
             }