diff --git a/sbin/gvinum/Makefile b/sbin/gvinum/Makefile
index 8cccf56ecdb..c9716e94670 100644
--- a/sbin/gvinum/Makefile
+++ b/sbin/gvinum/Makefile
@@ -5,7 +5,7 @@ SRCS=	gvinum.c gvinum.h geom_vinum_share.c
 MAN=	gvinum.8
 
 WARNS?=	2
-CFLAGS=	-I${.CURDIR}/../../sys -I${DESTDIR}/${INCLUDEDIR}/edit
+CFLAGS+=	-I${.CURDIR}/../../sys -I${DESTDIR}/${INCLUDEDIR}/edit
 
 DPADD=	${LIBEDIT} ${LIBTERMCAP} ${LIBDEVSTAT} ${LIBKVM} ${LIBGEOM}
 LDADD=	-ledit -ltermcap -ldevstat -lkvm -lgeom