diff --git a/usr.bin/less/Makefile b/usr.bin/less/Makefile
index 27415573a8e..ca9d948e1e4 100644
--- a/usr.bin/less/Makefile
+++ b/usr.bin/less/Makefile
@@ -19,5 +19,7 @@ LINKS=	${BINDIR}/less ${BINDIR}/more \
 MLINKS=	less.1 more.1
 CLEANFILES= less.1
 
+CFLAGS+=	${NO_WDEPRECATED_NON_PROTOTYPE}
+
 .include "Makefile.common"
 .include <bsd.prog.mk>