Simple IF condition makes the xlsx corrupt

[zprima]

I have

value = "=IF(A12>100;AC12;AC13)"
sheet.add_row [value]

and it makes the xlsx file corrupt, if i replace the value with SUM function SUM(A12:A13) just to test if functions work, it works fine. What am i missing? Oh and if i just copy paste the IF formula in excel also works fine.

used 3.0.0-pre, 2.1.0-pre, 2.0.1. All the same.

UPDATE:

replace ; with ,
value = "=IF(A12>100,AC12,AC13)"

solves the issue. amazing. end result in excel is with ;, which is super confusing