simgrid::s4u::Actor::on_destruction.connect([](simgrid::s4u::Actor const& actor) {
// free the data if a function was provided
- void* userdata = actor.extension<simgrid::msg::ActorUserData>()->get_user_data();
+ auto extension = actor.extension<simgrid::msg::ActorUserData>();
+ void* userdata = extension ? extension->get_user_data() : nullptr;
if (userdata && msg_global->process_data_cleanup) {
msg_global->process_data_cleanup(userdata);
}