Can't enter *#*#4636#*#* Android service menu after OxygenOS 1.0 update on OPO

After the upgrade, when I try to enter the menu by typing that on the dial pad, it clears the code after the second #. I'm guessing this is a feature designed to prevent filthy casuals messing with their phones, how do I turn it off?

Flash either an older version or another custom rom.