diff --git a/ch32v003fun/ch32v003fun.mk b/ch32v003fun/ch32v003fun.mk
index 8d39c567534b7f7dc045a8ca3b72f069d749aa08..b416c7fc6777e33c618349e5fc38d151769f0516 100644
--- a/ch32v003fun/ch32v003fun.mk
+++ b/ch32v003fun/ch32v003fun.mk
@@ -17,8 +17,9 @@ CFLAGS+= \
 LDFLAGS+=-T $(CH32V003FUN)/ch32v003fun.ld -Wl,--gc-sections -L$(CH32V003FUN)/../misc -lgcc
 
 SYSTEM_C:=$(CH32V003FUN)/ch32v003fun.c
+TARGET_EXT?=c
 
-$(TARGET).elf : $(SYSTEM_C) $(TARGET).c $(ADDITIONAL_C_FILES)
+$(TARGET).elf : $(SYSTEM_C) $(TARGET).$(TARGET_EXT) $(ADDITIONAL_C_FILES)
 	$(PREFIX)-gcc -o $@ $^ $(CFLAGS) $(LDFLAGS)
 
 $(TARGET).bin : $(TARGET).elf