diff --git a/index.js b/index.js
index 9106e64..05aac23 100644
--- a/index.js
+++ b/index.js
@@ -49,7 +49,8 @@ var USER_PASS_REGEXP = /^([^:]*):(.*)$/
  * Parse the Authorization header field of a request.
  *
  * @param {object} req
- * @return {object} with .name and .pass
+ * @throws {TypeError}
+ * @returns {(Credentials|undefined)}
  * @public
  */