diff --git a/knockout/knockout.d.ts b/knockout/knockout.d.ts
index c68c38aff5..6f9ff20763 100644
--- a/knockout/knockout.d.ts
+++ b/knockout/knockout.d.ts
@@ -306,7 +306,7 @@ interface KnockoutUtils {
 
     triggerEvent(element: any, eventType: any): void;
 
-    unwrapObservable<T>(value: KnockoutObservable<T>): T;
+    unwrapObservable<T>(value: KnockoutObservable<T> | T): T;
 
     peekObservable<T>(value: KnockoutObservable<T>): T;