[![Only button with label has linked style][1]][1] Only button with label has linked style. var button_box = new Gtk.Box (Gtk.Orientation.HORIZONTAL, 0); button_box.get_style_context ().add_class (Gtk.STYLE_CLASS_LINKED); info_button = new Gtk.Button.from_icon_name ("dialog-information-symbolic", Gtk.IconSize.LARGE_TOOLBAR); button_box.add (info_button); button_with_label = new Gtk.Button.with_label (_("Test")); button_box.add (button_with_label); header_bar.pack_start (button_box); [1]: https://i.sstatic.net/wUOxe.png