--- a/relnotes/next	Wed Sep 11 17:41:13 2019 +0200
+++ b/relnotes/next	Thu Sep 12 21:22:59 2019 -0700
@@ -22,5 +22,9 @@
    you can override it by setting `$HGTEST_SHELL` or by passing it to
    `run-tests.py --shell <shell>`.
 
+ * The (experimental) narrow extension's wire protocol changed. If
+   you're using it, you'll need to make sure to upgrade server and
+   client at the same time.
+
 == Internal API Changes ==