diff --git a/src/Avalonia.Themes.Default/DefaultTheme.xaml b/src/Avalonia.Themes.Default/DefaultTheme.xaml
index e5b654b490..c80d67cb6c 100644
--- a/src/Avalonia.Themes.Default/DefaultTheme.xaml
+++ b/src/Avalonia.Themes.Default/DefaultTheme.xaml
@@ -13,6 +13,7 @@
   <StyleInclude Source="resm:Avalonia.Themes.Default.ComboBox.xaml?assembly=Avalonia.Themes.Default"/>
   <StyleInclude Source="resm:Avalonia.Themes.Default.ComboBoxItem.xaml?assembly=Avalonia.Themes.Default"/>
   <StyleInclude Source="resm:Avalonia.Themes.Default.ContentControl.xaml?assembly=Avalonia.Themes.Default"/>
+  <StyleInclude Source="resm:Avalonia.Themes.Default.FontIcon.xaml?assembly=Avalonia.Themes.Default" />
   <StyleInclude Source="resm:Avalonia.Themes.Default.GridSplitter.xaml?assembly=Avalonia.Themes.Default"/>
   <StyleInclude Source="resm:Avalonia.Themes.Default.ItemsControl.xaml?assembly=Avalonia.Themes.Default"/>
   <StyleInclude Source="resm:Avalonia.Themes.Default.ListBox.xaml?assembly=Avalonia.Themes.Default"/>
diff --git a/src/Avalonia.Themes.Fluent/FluentTheme.xaml b/src/Avalonia.Themes.Fluent/FluentTheme.xaml
index 00ab9bc375..5fe1363980 100644
--- a/src/Avalonia.Themes.Fluent/FluentTheme.xaml
+++ b/src/Avalonia.Themes.Fluent/FluentTheme.xaml
@@ -12,6 +12,7 @@
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/ComboBox.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/ComboBoxItem.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/ContentControl.xaml"/>
+  <StyleInclude Source="avares://Avalonia.Themes.Fluent/FontIcon.xaml" />
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/GridSplitter.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/ItemsControl.xaml"/>
   <StyleInclude Source="avares://Avalonia.Themes.Fluent/ListBox.xaml"/>