diff --git a/src/ExNavigationRouter.js b/src/ExNavigationRouter.js
index 1eb9625..9ca01d0 100644
--- a/src/ExNavigationRouter.js
+++ b/src/ExNavigationRouter.js
@@ -334,7 +334,7 @@ export function createRouter<RC: RouteCreator>(
   return new ExNavigationRouter(routesCreator, options);
 }
 
-function _isSerializable(obj: Object): boolean {
+const _isSerializable = (obj) => {
   if (
     _.isUndefined(obj) ||
     _.isNull(obj) ||
@@ -356,4 +356,4 @@ function _isSerializable(obj: Object): boolean {
   }
 
   return true;
-}
+};