Reported by Hernando Torque here:
https://bugzilla.gnome.org/show_bug.cgi?id=616851
/**
* gtk_tool_button_new:
* @label: (allow-none): a string that will be used as label, or %NULL
- * @icon_widget: (allow-none): a widget that will be used as icon widget, or %NULL
+ * @icon_widget: (allow-none): a #GtkMisc widget that will be used as icon widget, or %NULL
*
* Creates a new %GtkToolButton using @icon_widget as icon and @label as
* label.
{
GtkToolButton *button;
+ g_return_val_if_fail (GTK_IS_MISC (icon_widget), NULL);
+
button = g_object_new (GTK_TYPE_TOOL_BUTTON,
"label", label,
"icon-widget", icon_widget,