diff --git a/lib/6to5/browser.js b/lib/6to5/browser.js
index acc8ea0261..4f51333e4e 100644
--- a/lib/6to5/browser.js
+++ b/lib/6to5/browser.js
@@ -1,3 +1,5 @@
+// this is gross but it polyfills in behaviour required by `depd` used by
+// `ast-types`
 Error.captureStackTrace = Error.captureStackTrace || function (obj) {
   if (Error.prepareStackTrace) {
     var frame = {