During install MacBookAir5,2 screen goes blank, need external monitor

[Sevan / Venture37]

Hi,
It's doesn't seem to be possible to use the screen on the MacBook Air to 
install OpenBSD.
While the screen works initially, by the time you have reached the 
choosing disk sets to install, the screen will go blank.
Connecting an external monitor to the thunderbolt port can prolong the 
process so that you install completes, the laptop screen will function 
as normal in X11 when booted from the stock bsd.mp kernel.

I need to double check if the issue still occurs without X11 on a stock 
kernel.

Is this a known issue & if so is there any way not requiring a external 
monitor??


Sevan / Venture37