diff --git a/demos/ARMCM3-STM32F103-GCC/Makefile b/demos/ARMCM3-STM32F103-GCC/Makefile
index e4c34fadb..28a353c37 100644
--- a/demos/ARMCM3-STM32F103-GCC/Makefile
+++ b/demos/ARMCM3-STM32F103-GCC/Makefile
@@ -128,7 +128,7 @@ CPPC = $(TRGT)g++
 LD   = $(TRGT)gcc
 #LD   = $(TRGT)g++
 CP   = $(TRGT)objcopy
-AS   = $(TRGT)gcc
+AS   = $(TRGT)gcc -x assembler-with-cpp
 OD   = $(TRGT)objdump
 HEX  = $(CP) -O ihex
 BIN  = $(CP) -O binary