diff --git a/packages/react-navigation/flow/react-navigation.js b/packages/react-navigation/flow/react-navigation.js
index 640ba845..98b5c3aa 100644
--- a/packages/react-navigation/flow/react-navigation.js
+++ b/packages/react-navigation/flow/react-navigation.js
@@ -533,7 +533,7 @@ declare module 'react-navigation' {
       eventName: string,
       callback: NavigationEventCallback
     ) => NavigationEventSubscription,
-    getParam: <ParamName>(
+    getParam: <ParamName: string>(
       paramName: ParamName,
       fallback?: $ElementType<
         $PropertyType<