diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 9ecea37ad4..cc32c49f0f 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -94,6 +94,7 @@ def get_mcu_lib(mcu):
 
 def setup_mcu_type_defaults():
     '''setup defaults for given mcu type'''
+    global pincount
     lib = get_mcu_lib(mcu_type)
     if hasattr(lib, 'pincount'):
         pincount = lib.pincount