diff --git a/npm/index.js b/npm/index.js
index ce9a284..4bdaddd 100644
--- a/npm/index.js
+++ b/npm/index.js
@@ -108,6 +108,7 @@ async function transform(json, code) {
   }
 
   const fn = eval(`(function () {
+    const x = this
     return ${code}
   })`).call(json)