diff --git a/Makefile b/Makefile
index 3001b61..1165710 100644
--- a/Makefile
+++ b/Makefile
@@ -2,14 +2,15 @@ CC      =   $(CROSS_COMPILE)gcc
 CPP     =   $(CROSS_COMPILE)cpp
 AR      =   $(CROSS_COMPILE)ar
 LD      =   $(CROSS_COMPILE)ld
-OBJCOPY     =   $(CROSS_COMPILE)objcopy
-OBJDUMP     =   $(CROSS_COMPILE)objdump
-CFLAGS = -fPIC -fno-stack-protector
+OBJCOPY =   $(CROSS_COMPILE)objcopy
+OBJDUMP =   $(CROSS_COMPILE)objdump
+XLEN	:=	$(shell $(CC) -dM -E - < /dev/null | grep '__riscv_xlen' | awk '{print $$3}')
+CFLAGS = -march=rv$(XLEN)gc -fPIC -fno-stack-protector -O0
 TARGET = zero_stage_boot
 ${TARGET}.elf: start.o feature.o jump.o
 	$(LD) $(CROSS_LDFLAGS) -Tlink.lds $^ -o $@
 	$(OBJCOPY) -O binary $@ ${TARGET}.bin
-	$(OBJDUMP) -D $@ > ${TARGET}.asm
+	$(OBJDUMP) -S $@ > ${TARGET}.asm
 
 %.o: %.c
 	$(CC) -mcmodel=medany ${CFLAGS} -g -c $^