diff --git a/knockout.postbox/knockout-postbox.d.ts b/knockout.postbox/knockout-postbox.d.ts
index 21c10382e..341e817cb 100644
--- a/knockout.postbox/knockout-postbox.d.ts
+++ b/knockout.postbox/knockout-postbox.d.ts
@@ -1,6 +1,7 @@
 interface KnockoutPostBox {
     subscribe: (topic: string, handler: (value) => void, target?: any) => KnockoutObservableAny;
     publish: (topic: string, value?: any) => KnockoutObservableAny;
+    defaultComparer: (newValue: any, oldValue: any) => bool;
 }
 
 interface KnockoutObservableString {