Staircase progression if first response is incorrect

I’m trying to run a task where if the participant selects the right answer, it goes down by one level, but if they get the wrong answer it goes back by 2 level. Currently I have my staircase step size set to [1,2], and it works if you get the first response correct (starts at level 11, and ranges from level 13 to level 0). However if you get the first prompt wrong, then it does the opposite of what I want (up by one level and down by 2) e.g. want it to do 11-©->10-©->9-©->8-(ic)->10-©->9 etc. but is doing this: 11-(ic)->12-©->10-©->8-(ic)->9-©->7 etc
Thank you!