diff --git a/knockout/knockout.d.ts b/knockout/knockout.d.ts
index 5ae7c13ea7..a43ac908a5 100644
--- a/knockout/knockout.d.ts
+++ b/knockout/knockout.d.ts
@@ -242,6 +242,7 @@ interface KnockoutVirtualElements {
 interface KnockoutExtenders {
     throttle(target: any, timeout: number): KnockoutComputed;
     notify(target: any, notifyWhen: string): any;
+    logChange: (target: KnockoutObservableAny, option: string) => KnockoutObservableAny;
 }
 
 interface KnockoutUtils {
@@ -530,4 +531,4 @@ interface KnockoutStatic {
     bindingProvider: any;
 }
 
-declare var ko: KnockoutStatic;
+declare var ko: KnockoutStatic;