diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F732xx.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F732xx.py
index 90296e9f2b..f510de7bd9 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F732xx.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/STM32F732xx.py
@@ -12,9 +12,6 @@ build = {
 
 # MCU parameters
 mcu = {
-    # location of MCU serial number
-    'UDID_START' : 0x1FF07A10,
-
     # ram map, as list of (address, size-kb, flags)
     # flags of 1 means DMA-capable
     # flags of 2 means faster memory for CPU intensive work
diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 24a0f9a294..49f65919cd 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -779,7 +779,11 @@ def write_mcu_config(f):
         f.write('#define HAL_RAM_RESERVE_START 0x%08x\n' % ram_reserve_start)
 
     f.write('\n// CPU serial number (12 bytes)\n')
-    f.write('#define UDID_START 0x%08x\n\n' % get_mcu_config('UDID_START', True))
+    udid_start = get_mcu_config('UDID_START')
+    if udid_start is None:
+        f.write('#define UDID_START UID_BASE\n\n')
+    else:
+        f.write('#define UDID_START 0x%08x\n\n' % udid_start)
 
     f.write('\n// APJ board ID (for bootloaders)\n')
     f.write('#define APJ_BOARD_ID %s\n' % get_config('APJ_BOARD_ID'))