Custom BBCodes not working after converting from phpBB 2

Custom BBCodes in old posts converted from phpBB 2 aren’t parsed. I need to manually edit every old post and send it unchanged to see custom BBcodes work. There’s what I did:

1. I’ve made fresh installation of 3.2.1‐RC1.
2. I added custom BBCodes present on my old board running phpBB 2.
3. I used bulit‐in convertor to convert my phpBB 2 database into phpBB 3.2.