diff --git a/cddl/usr.sbin/lockstat/Makefile b/cddl/usr.sbin/lockstat/Makefile
index 0668758c2f97..499b23db23b8 100644
--- a/cddl/usr.sbin/lockstat/Makefile
+++ b/cddl/usr.sbin/lockstat/Makefile
@@ -18,6 +18,7 @@ CFLAGS+=	-I${.CURDIR}/../../../sys/cddl/compat/opensolaris \
 		-I${.CURDIR}/../../../sys
 
 CFLAGS+=	-DNEED_ERRLOC -g
+CSTD?=		gnu99
 
 #YFLAGS+=	-d