diff --git a/src/platforms/swlink/Makefile.inc b/src/platforms/swlink/Makefile.inc
index ca793d45..0ca2a3b2 100644
--- a/src/platforms/swlink/Makefile.inc
+++ b/src/platforms/swlink/Makefile.inc
@@ -2,6 +2,7 @@ CROSS_COMPILE ?= arm-none-eabi-
 CC = $(CROSS_COMPILE)gcc
 OBJCOPY = $(CROSS_COMPILE)objcopy
 
+OPT_FLAGS = -Os
 CFLAGS += -mcpu=cortex-m3 -mthumb \
 	-DSTM32F1 -DDISCOVERY_SWLINK -I../libopencm3/include \
 	-I platforms/stm32