pin PB9 is reserved for CAN

[wjcloudy]

Trying to use Stepper motor 4 - the step pin for this is connected to PB9 (confirmed by manual and sample config)

However klipper rejects this with the error: "pin PB9 is reserved for CAN"

Any ideas? (Schematic says can is on PD1 and PD0)

using USB to CAN bridge mode (USB on PA11/PA12). If I disable can by flashing USB mode, then it works - but I'd like to use onboard can for the toolhead....