diff --git a/lib/installer.js b/lib/installer.js
index 0aebc77..bc3cc38 100644
--- a/lib/installer.js
+++ b/lib/installer.js
@@ -129,6 +129,7 @@ const checkFilenameForLine = async (filename, line) => {
  * @param {String} options.scriptname - The line to add sourcing this file.
  * @param {String} options.name - The package being configured.
  * @param {String} options.shell
+ * @returns {Promise.<void>}
  */
 const writeLineToFilename = ({ filename, scriptname, name, shell }) => new Promise((
   resolve,