diff --git a/src/util.ts b/src/util.ts
index 8fac69316..94be23477 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -166,9 +166,13 @@ export function convertVersionToSemver(version: number[] | string) {
 export function getGitHubHttpHeaders(): OutgoingHttpHeaders {
   const token = core.getInput('token');
   const auth = !token ? undefined : `token ${token}`;
+
   const headers: OutgoingHttpHeaders = {
-    authorization: auth,
     accept: 'application/vnd.github.VERSION.raw'
   };
+
+  if (auth) {
+    headers.authorization = auth;
+  }
   return headers;
 }