diff --git a/lib/create-tree.js b/lib/create-tree.js
index 84940e5a3b..5b371d372f 100644
--- a/lib/create-tree.js
+++ b/lib/create-tree.js
@@ -3,6 +3,8 @@ const path = require('path')
 const Page = require('./page')
 
 module.exports = async function createTree (originalPath, langObj) {
+  // This basePath definition is needed both here and in lib/page-data.js because this
+  // function runs recursively, and the value for originalPath changes on recursive runs.
   const basePath = path.posix.join(__dirname, '..', langObj.dir, 'content')
 
   // On recursive runs, this is processing page.children items in `/<link>` format.