[Vala] Gtk+ -mwindows

[Stamper <stamper ukr net>]

Hello!

I learn Vala now. I use win32 binaries from 
http://www.tarnyko.net/en/?q=node/13 and Geany as IDE.
I'm trying to develop simple Gtk UI application. But I want to hide 
windows promt console. I've found this:
http://stackoverflow.com/questions/2281514/how-to-hide-command-prompt-for-my-windows-gtk-apps
>>You have to specify -mwindows at compile time.

But it does not work in command promt like this: "d:\vala\src> valac 
--pkg gtk+-3.0 -mwindows gtkdemo.vala"
What am I doing wrong? How I should to specify "-mwindows" at compile time?

Thank you!

--
WBR, Stamper