diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index ffef024682..eb5dd6776e 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -797,12 +797,20 @@ def parse_i2c_device(dev):
     busnum = int(a[1])
     return ('', 'GET_I2C_DEVICE(%u,0x%02x)' % (busnum, busaddr))
 
+def seen_str(dev):
+    '''return string representation of device for checking for duplicates'''
+    return str(dev[:2])
+
 def write_IMU_config(f):
     '''write IMU config defines'''
     global imu_list
     devlist = []
     wrapper = ''
+    seen = set()
     for dev in imu_list:
+        if seen_str(dev) in seen:
+            error("Duplicate IMU: %s" % seen_str(dev))
+        seen.add(seen_str(dev))
         driver = dev[0]
         for i in range(1,len(dev)):
             if dev[i].startswith("SPI:"):
@@ -818,10 +826,14 @@ def write_IMU_config(f):
         f.write('#define HAL_INS_PROBE_LIST %s\n\n' % ';'.join(devlist))
 
 def write_MAG_config(f):
-    '''write IMU config defines'''
+    '''write MAG config defines'''
     global compass_list
     devlist = []
+    seen = set()
     for dev in compass_list:
+        if seen_str(dev) in seen:
+            error("Duplicate MAG: %s" % seen_str(dev))
+        seen.add(seen_str(dev))
         driver = dev[0]
         probe = 'probe'
         wrapper = ''
@@ -846,7 +858,11 @@ def write_BARO_config(f):
     '''write barometer config defines'''
     global baro_list
     devlist = []
+    seen = set()
     for dev in baro_list:
+        if seen_str(dev) in seen:
+            error("Duplicate BARO: %s" % seen_str(dev))
+        seen.add(seen_str(dev))
         driver = dev[0]
         probe = 'probe'
         wrapper = ''