diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/chibios_board.mk b/libraries/AP_HAL_ChibiOS/hwdef/common/chibios_board.mk
index 174b5f69f0..eb6e103d97 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/chibios_board.mk
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/chibios_board.mk
@@ -5,12 +5,12 @@
 
 # Compiler options here.
 ifeq ($(USE_OPT),)
-  USE_OPT = -Os -g -fomit-frame-pointer -falign-functions=16
+  USE_OPT = -g -fomit-frame-pointer -falign-functions=16
 endif
 
 # C specific options here (added to USE_OPT).
 ifeq ($(USE_COPT),)
-  USE_COPT =
+  USE_COPT = -Os
 endif
 
 # C++ specific options here (added to USE_OPT).