[1.7.10] Any reason this code is not opening the GUI

I don't get why this isn't working!

	public boolean onBlockActivated(World world, int x, int y, int z, EntityPlayer player, int p_149727_6_, float p_149727_7_, float p_149727_8_, float p_149727_9_) {
	if (!world.isRemote) {
		player.displayGUIWorkbench(x, y, z);
	}
	return true;
}