diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 8d6ec23f37..353523e913 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -1488,6 +1488,11 @@ def write_IMU_config(f):
             error("Duplicate IMU: %s" % seen_str(dev))
         seen.add(seen_str(dev))
         driver = dev[0]
+        # get instance number if mentioned
+        instance = -1
+        if dev[-1].startswith("INSTANCE:"):
+            instance = int(dev[-1][9:])
+            dev = dev[:-1]
         for i in range(1, len(dev)):
             if dev[i].startswith("SPI:"):
                 dev[i] = parse_spi_device(dev[i])
@@ -1495,7 +1500,11 @@ def write_IMU_config(f):
                 (wrapper, dev[i]) = parse_i2c_device(dev[i])
         n = len(devlist)+1
         devlist.append('HAL_INS_PROBE%u' % n)
-        if dev[-1].startswith("BOARD_MATCH("):
+        if instance != -1:
+            f.write(
+            '#define HAL_INS_PROBE%u %s ADD_BACKEND_INSTANCE(AP_InertialSensor_%s::probe(*this,%s),%d)\n'
+            % (n, wrapper, driver, ','.join(dev[1:]), instance))
+        elif dev[-1].startswith("BOARD_MATCH("):
             f.write(
                 '#define HAL_INS_PROBE%u %s ADD_BACKEND_BOARD_MATCH(%s, AP_InertialSensor_%s::probe(*this,%s))\n'
                 % (n, wrapper, dev[-1], driver, ','.join(dev[1:-1])))