DE1-SOC power button non-functioning in AS/EPCS mode

Apologies if this has been answered elsewhere, I seem to have read about the issue but can't locate my source now.

I've transferred my design to EPCS memory of the DE1-SOC board. Now regardless of the state of the red power button, whenever I plug in the DC adaptor, the board comes up immediately with no way apparently to switch it off except pulling the plug.

I liked being able to power up/down the board using the red button while using JTAG mode, can it not be used in AS mode at all? Can I power the board down under software-control?