diff --git a/ui/PRESUBMIT.py b/ui/PRESUBMIT.py
index eecdfeb..a4d6df0 100644
--- a/ui/PRESUBMIT.py
+++ b/ui/PRESUBMIT.py
@@ -53,6 +53,9 @@
     return [
         output_api.PresubmitError("""\
 There were tslint errors. You may be able to fix some of them using
-$ {} {} --project {} --fix""".format(relpath(node), relpath(tslint), ui_path))
+$ {} {} --project {} --fix
+
+If this is unexpected: did you remember to do a UI build before running the
+presubmit?""".format(relpath(node), relpath(tslint), ui_path))
     ]
   return []