The static construct block of a class is executed before a new object of that type is created. However I would expect it to be executed when static methods are called.

Example:

/* 
 * valac test.vala
 */

using GLib;

public class Statico : GLib.Object {
	public static int test_value;

	static construct {
		test_value = 5;
	}

	public static int get_test_value() {
		return test_value;
	}
}


public class Test : GLib.Object {
	public static void main(string[] args) {
		/* Should print '5', but prints '0' */
		stdout.printf("%d\n", Statico.get_test_value());
	}
}