Index: head/security/seal/Makefile
===================================================================
--- head/security/seal/Makefile	(revision 495564)
+++ head/security/seal/Makefile	(revision 495565)
@@ -1,21 +1,21 @@
 # $FreeBSD$
 
 PORTNAME=	seal
 PORTVERSION=	3.1.0
 CATEGORIES=	security
 
 MAINTAINER=	lwhsu@FreeBSD.org
 COMMENT=	Microsoft Simple Encrypted Arithmetic Library
 
 LICENSE=	MIT
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
-USES=	cmake
+USES=		cmake compiler:c++17-lang
 
 CMAKE_SOURCE_PATH=	${WRKSRC}/src
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	Microsoft
 GH_PROJECT=	SEAL
 
 .include <bsd.port.mk>