diff --git a/theme/upgrade.txt b/theme/upgrade.txt
index e8622a54c9a..3fe058adba5 100644
--- a/theme/upgrade.txt
+++ b/theme/upgrade.txt
@@ -9,6 +9,10 @@ information provided here is intended especially for theme designer.
 * Meta description is now included in standard_head_html for homepage in bootstrapbase.
   If your theme includes a meta description directly in a layout for the frontpage,
   you will need to remove it or override the standard_head_html instead.
+* Themes Clean and More have been updated to use a new navbar_button function, which shows the
+  hamburguer icon (responsive menu) or not depending on custom and language menus settings;
+  themes extending bootstrapbase and overriding its layouts can call replace their "a.btn-navbar"
+  node for a call to this function.
 
 === 2.9 ===