Index: head/math/libxls/Makefile
===================================================================
--- head/math/libxls/Makefile	(revision 503883)
+++ head/math/libxls/Makefile	(revision 503884)
@@ -1,19 +1,19 @@
 # $FreeBSD$
 
 PORTNAME=	libxls
 PORTVERSION=	1.5.1
 CATEGORIES=	math devel
 MASTER_SITES=	https://github.com/${PORTNAME}/${PORTNAME}/releases/download/v${PORTVERSION}/
 
 MAINTAINER=	bapt@FreeBSD.org
 COMMENT=	Extract Cell Data From Excel xls files
 
 LICENSE=	BSD2CLAUSE
 
-USES=	libtool
+USES=	compiler:c++11-lang libtool
 
 GNU_CONFIGURE=	yes
 INSTALL_TARGET=	install-strip
 USE_LDCONFIG=	yes
 
 .include <bsd.port.mk>