diff --git a/src/client.ts b/src/client.ts
index 8f973c0..08e24e7 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -385,8 +385,8 @@ export class Gitpod {
     return;
   }
 
-  protected authHeaders(opts: FinalRequestOptions): Headers | undefined {
-    return new Headers({ Authorization: `Bearer ${this.bearerToken}` });
+  protected authHeaders(opts: FinalRequestOptions): NullableHeaders | undefined {
+    return buildHeaders([{ Authorization: `Bearer ${this.bearerToken}` }]);
   }
 
   /**