diff --git a/WHATSNEW.md b/WHATSNEW.md
index ede6bba95..3247d03fc 100644
--- a/WHATSNEW.md
+++ b/WHATSNEW.md
@@ -1,5 +1,9 @@
 ## V4.10.3
 
+### Important note
+- The main class name for the `FluentAppBar` component has been renamed from `nav-menu-container` to `fluent-appbar`. If you have custom CSS in your app targeting that class, you need to change that to you the new class name.
+
+
 ### General
 - \[General\] Apply global color-scheme to reflect theme in use ([#2854](https://github.com/microsoft/fluentui-blazor/pull/2854))
 
diff --git a/examples/Demo/Shared/wwwroot/docs/WhatsNew.md b/examples/Demo/Shared/wwwroot/docs/WhatsNew.md
index 6899bade2..5119b6cb0 100644
--- a/examples/Demo/Shared/wwwroot/docs/WhatsNew.md
+++ b/examples/Demo/Shared/wwwroot/docs/WhatsNew.md
@@ -1,5 +1,8 @@
 ## V4.10.3
 
+### Important note
+- The main class name for the `FluentAppBar` component has been renamed from `nav-menu-container` to `fluent-appbar`. If you have custom CSS in your app targeting that class, you need to change that to you the new class name.
+
 ### General
 - \[General\] Apply global color-scheme to reflect theme in use ([#2854](https://github.com/microsoft/fluentui-blazor/pull/2854))