diff --git a/Makefile b/Makefile
index ca22379d7..3b1890d1d 100644
--- a/Makefile
+++ b/Makefile
@@ -38,8 +38,8 @@ default: $(PROG)
 arch_flags : arch_flags.c
 	$(CC) arch_flags.c -o arch_flags
 
-ARCHFLAGS := $(shell $(CC) arch_flags.c -o arch_flags && ./arch_flags)
-OPTFLAGS  := -g -O #-DABC_NAMESPACE=xxx
+ARCHFLAGS ?= $(shell $(CC) arch_flags.c -o arch_flags && ./arch_flags)
+OPTFLAGS  ?= -g -O #-DABC_NAMESPACE=xxx
 
 CFLAGS   += -Wall -Wno-unused-function -Wno-write-strings -Wno-sign-compare $(OPTFLAGS) $(ARCHFLAGS) -I$(PWD)/src