diff --git a/gtk/gtkoverlay.c b/gtk/gtkoverlay.c
index b9208a9d7c..0af10a5c34 100644
--- a/gtk/gtkoverlay.c
+++ b/gtk/gtkoverlay.c
@@ -804,6 +804,8 @@ gtk_overlay_class_init (GtkOverlayClass *klass)
                   G_TYPE_BOOLEAN, 2,
                   GTK_TYPE_WIDGET,
                   GDK_TYPE_RECTANGLE | G_SIGNAL_TYPE_STATIC_SCOPE);
+
+  gtk_widget_class_set_css_name (widget_class, "overlay");
 }
 
 static void