diff --git a/packages/babel-core/src/config/option-manager.js b/packages/babel-core/src/config/option-manager.js
index b42199830b..6bd6757080 100644
--- a/packages/babel-core/src/config/option-manager.js
+++ b/packages/babel-core/src/config/option-manager.js
@@ -1,3 +1,5 @@
+// @flow
+
 import * as context from "../index";
 import Plugin from "./plugin";
 import * as messages from "babel-messages";