diff --git a/packages/react-navigation/flow/react-navigation.js b/packages/react-navigation/flow/react-navigation.js
index 096d04a8..b3d5c3b7 100644
--- a/packages/react-navigation/flow/react-navigation.js
+++ b/packages/react-navigation/flow/react-navigation.js
@@ -818,7 +818,7 @@ declare module 'react-navigation' {
       actions: Array<NavigationNavigateAction>,
     }) => NavigationResetAction,
     replace: (payload: {
-      key: string,
+      key?: string,
       routeName: string,
       params?: NavigationParams,
       action?: NavigationNavigateAction,