diff --git a/babel.config.js b/babel.config.js
index 51e5e99..6f292a1 100644
--- a/babel.config.js
+++ b/babel.config.js
@@ -1,3 +1,3 @@
-const presets = [["@babel/env", {}]];
+const presets = [["@babel/env", {}], ["@babel/preset-flow", {}]];
 
 module.exports = { presets };
diff --git a/src/mailgo.js b/src/mailgo.js
index d391b0a..e835256 100644
--- a/src/mailgo.js
+++ b/src/mailgo.js
@@ -1,3 +1,4 @@
+// @flow
 const V = "MAILGO_VERSION";
 const MAILTO = "mailto:";