error while setting outgoig multicast interface (IP_MULTICAST_IF)

[iliabaranov]

I keep getting the above error when launching on a bridge network:

sudo ptpd -i br0 -L -M -V
2022-02-08 16:58:12.835012 ptpd2[31029].startup (info)      (___) Configuration OK
2022-02-08 16:58:12.838644 ptpd2[31029].startup (notice)    (___) PTPDv2 started successfully on br0 using "masteronly" preset (PID 31029)
2022-02-08 16:58:12.838669 ptpd2[31029].startup (info)      (___) TimingService.PTP0: PTP service init
# Timestamp, State, Clock ID, One Way Delay, Offset From Master, Slave to Master, Master to Slave, Observed Drift, Last packet Received, One Way Delay Mean, One Way Delay Std Dev, Offset From Master M
ean, Offset From Master Std Dev, Observed Drift Mean, Observed Drift Std Dev, raw delayMS, raw delaySM
2022-02-08 16:58:12.838687, init, 
2022-02-08 16:58:12.847963 ptpd2[31029].br0 (error)     (init) error while setting outgoig multicast interface (IP_MULTICAST_IF)      (strerror: Invalid argument)
2022-02-08 16:58:12.848197 ptpd2[31029].br0 (error)     (init) Failed to initialize network
2022-02-08 16:58:12.848213, flt, 
2022-02-08 16:58:12.848220 ptpd2[31029].br0 (error)     (flt) PTPd init failed - will retry in 10 seconds
2022-02-08 16:58:12.848229, init, 
2022-02-08 16:58:22.838695 ptpd2[31029].br0 (notice)    (init) TimingService.PTP0: elected best TimingService
2022-02-08 16:58:22.838741 ptpd2[31029].br0 (info)      (init) TimingService.PTP0: acquired clock control
2022-02-08 16:58:23.071723 ptpd2[31029].br0 (error)     (init) error while setting outgoig multicast interface (IP_MULTICAST_IF)      (strerror: Invalid argument)
2022-02-08 16:58:23.072059 ptpd2[31029].br0 (error)     (init) Failed to initialize network
2022-02-08 16:58:23.072183, flt, 
2022-02-08 16:58:23.072192 ptpd2[31029].br0 (error)     (flt) PTPd init failed - will retry in 10 seconds
2022-02-08 16:58:23.072230, init,