diff --git a/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.PopupBox.xaml b/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.PopupBox.xaml
index e65875261b..367282c1b5 100644
--- a/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.PopupBox.xaml
+++ b/src/MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.PopupBox.xaml
@@ -12,7 +12,8 @@