diff --git a/libraries/AP_HAL_ChibiOS/hwdef/HolybroG4_GPS/hwdef.dat b/libraries/AP_HAL_ChibiOS/hwdef/HolybroG4_GPS/hwdef.dat
index c2d5beca9a014..9dd7533f6c2a1 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/HolybroG4_GPS/hwdef.dat
+++ b/libraries/AP_HAL_ChibiOS/hwdef/HolybroG4_GPS/hwdef.dat
@@ -74,9 +74,9 @@ define HAL_I2C_INTERNAL_MASK 3
 I2C_ORDER I2C1 I2C2
 
 # one SPI bus (for IMU, unused)
-#PA5 SPI1_SCK SPI1
-#PA6 SPI1_MISO SPI1
-#PA7 SPI1_MOSI SPI1
+PA5 SPI1_SCK SPI1
+PA6 SPI1_MISO SPI1
+PA7 SPI1_MOSI SPI1
 
 # SPI CS
 PC4  GYR_CS CS
@@ -134,10 +134,17 @@ DMA_NOSHARE USART3*
 # add support for moving baseline yaw
 define GPS_MOVING_BASELINE 1
 
+SPIDEV icm42688  SPI1  DEVID1  ICM_CS   MODE0  24*MHZ  24*MHZ
+
+IMU Invensensev3 SPI:icm42688 ROTATION_YAW_180
+
+define HAL_PERIPH_ENABLE_IMU
+
 # GPS+MAG+LEDs
 define HAL_PERIPH_ENABLE_GPS
 define HAL_PERIPH_ENABLE_MAG
 define HAL_PERIPH_ENABLE_BARO
+define HAL_PERIPH_ENABLE_IMU
 define HAL_PERIPH_ENABLE_NOTIFY
 define HAL_PERIPH_ENABLE_RC_OUT