diff --git a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
index 927ddf861d..5730f68585 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
+++ b/libraries/AP_HAL_ChibiOS/hwdef/scripts/chibios_hwdef.py
@@ -411,10 +411,15 @@ class ChibiOSHWDef(object):
                 self.type.startswith('UART')) and (
                 (self.label.endswith('_TX') or
                  self.label.endswith('_RX') or
-                 self.label.endswith('_CTS') or
-                 self.label.endswith('_RTS'))):
+                 self.label.endswith('_CTS'))):
                 v = "PULLUP"
 
+            # pulldown on RTS to prevent radios from staying in bootloader
+            if (self.type.startswith('USART') or
+                self.type.startswith('UART')) and (
+                 self.label.endswith('_RTS')):
+                v = "PULLDOWN"
+
             if (self.type.startswith('SWD') and
                     'SWDIO' in self.label):
                 v = "PULLUP"