From Canon USA:
Firmware Version 1.1.1 incorporates the following enhancements and fixes:
- The option to capture both 4K and Full HD movies in the frame rate of 23.98p has been newly added.
- Fixes an issue where error code "Err 01" may be displayed when using EF85mm F1.8 USM or EF100mm F2 USM lenses.
Download: Canon EOS 90D Firmware v.1.1.1