diff --git a/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F405/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F405/hwdef.dat
index e44d80a0df..dfd4ffa397 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F405/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F405/hwdef.dat
@@ -102,6 +102,7 @@ define HAL_PERIPH_ENABLE_MAG
 
 SPIDEV  rm3100 SPI1 DEVID1   MAG_CS MODE0  1*MHZ  1*MHZ
 COMPASS RM3100 SPI:rm3100 false ROTATION_PITCH_180
+define AP_RM3100_REVERSAL_MASK 7
 define HAL_COMPASS_MAX_SENSORS 1
 
 # --------------------- DPS310 ---------------------------
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F412/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F412/hwdef.dat
index 040ab4caac..0aa12aaf5d 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F412/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/Sierra-F412/hwdef.dat
@@ -69,6 +69,7 @@ BARO DPS310 SPI:dps310
 # Mag probe
 SPIDEV  rm3100 SPI1 DEVID1   MAG_CS MODE0  1*MHZ  1*MHZ
 COMPASS RM3100 SPI:rm3100 false ROTATION_PITCH_180
+define AP_RM3100_REVERSAL_MASK 7
 
 # PWM, WS2812 LED
 PB8 TIM4_CH3 TIM4 PWM(1) GPIO(50)