diff --git a/src/index.js b/src/index.js
index 015ba6bb4..207f689d2 100644
--- a/src/index.js
+++ b/src/index.js
@@ -136,7 +136,7 @@ async function fetchToken(wwwAuthenticate, scope, authorization) {
   if (scope) {
     url.searchParams.set("scope", scope);
   }
-  headers = new Headers();
+  const headers = new Headers();
   if (authorization) {
     headers.set("Authorization", authorization);
   }