diff --git a/src/ac/Makefile b/src/ac/Makefile
index 0cc25599..b8b658ec 100644
--- a/src/ac/Makefile
+++ b/src/ac/Makefile
@@ -11,7 +11,7 @@ ifndef ARCH
 endif
 
 LDFLAGS+=-g -D_REENTRANT -L/usr/local/lib -L../capwap/$(ARCH)
-CFLAGS += -Werror -g -O0 -D_REENTRANT -DIPV6 -I/usr/local/include -I../
+CFLAGS += -Werror -g -O0 -D_REENTRANT -DIPV6 -I/usr/local/include -I../ -DSYS_ARCH=\"${ARCH}\"
 
 
 LIBS+=-lcapwap