[Vala] Thread error 'assignment makes pointer from integer without a cast'

[David M <dmlh02 gmail com>]

Following upgrading to Vala verion 0.15.2, I get the warning 'GLib.Thread.create 
has been deprecated since 2.32. Use new Thread<T> ()'. So I did as it suggested, 
but then I get the errors as follows:

In function ?thread_demo_main?:
warning: assignment makes pointer from integer without a cast [enabled by 
default]
undefined reference to `g_thread_new'
undefined reference to `g_thread_free'

An example of code to recreate these errors is as follows:

public class ThreadDemo {
        
        public static void main (string [] args) {
                
                ThreadDemo demo = new ThreadDemo();
                Thread<void*> thread_a = new Thread<void*> 
                        (null, demo.thread_func);
                thread_a.join ();
                
        }
        
        public void* thread_func () {
                print ("hello from the thread function.\n");
                void* ret = null;
                return ret;
        }
        
}

Is this a bug in Vala or am I phrasing the call incorrectly?

Thanks,

David