diff --git a/libraries/AP_HAL/board/chibios.h b/libraries/AP_HAL/board/chibios.h
index cb545ee7bf..16cd1960eb 100644
--- a/libraries/AP_HAL/board/chibios.h
+++ b/libraries/AP_HAL/board/chibios.h
@@ -104,7 +104,9 @@
 #endif
 
 // we support RC serial for BLHeli pass-thru
+#ifndef HAL_SUPPORT_RCOUT_SERIAL
 #define HAL_SUPPORT_RCOUT_SERIAL 1
+#endif
 
 // by default assume first I2C bus is internal
 #ifndef HAL_I2C_INTERNAL_MASK