diff --git a/lib/cli/collect-files.js b/lib/cli/collect-files.js
index e5ae32486a..2def30d5af 100644
--- a/lib/cli/collect-files.js
+++ b/lib/cli/collect-files.js
@@ -53,6 +53,7 @@ module.exports = ({
     }
   }, []);
 
+  // check that each file passed in to --file exists
   fileArgs.forEach(file => {
     try {
       require.resolve(file);