diff --git a/knockout.mapping/knockout.mapping.d.ts b/knockout.mapping/knockout.mapping.d.ts
index 69b6ccaffb..010f188012 100644
--- a/knockout.mapping/knockout.mapping.d.ts
+++ b/knockout.mapping/knockout.mapping.d.ts
@@ -13,7 +13,7 @@ interface KnockoutMappingCreateOptions {
 interface KnockoutMappingUpdateOptions {
     data: any;
     parent: any;
-    observable: KnockoutObservableAny;
+    observable: KnockoutObservable<any>;
 }
 
 interface KnockoutMappingOptions {