diff --git a/tests/run.js b/tests/run.js
index d5c58f2..735993a 100644
--- a/tests/run.js
+++ b/tests/run.js
@@ -1,3 +1,5 @@
+// @flow
+
 import * as assert from 'assert';
 import * as fs from 'fs';
 import * as path from 'path';