diff --git a/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/hwdef.dat
index e273b7fdc5..663a3bca8d 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/Pixhawk4/hwdef.dat
@@ -3,3 +3,6 @@
 
 include ../fmuv5/hwdef.dat
 
+# use ChibiOS based IO firmware to avoid issue with SBUS
+# input. NuttX has no parity checking on UARTs
+ROMFS io_firmware.bin Tools/IO_Firmware/fmuv2_IO_ChibiOS.bin