diff --git a/math/blahtexml/Makefile b/math/blahtexml/Makefile
index f86f51ff37ec..3619a4cf7b1a 100644
--- a/math/blahtexml/Makefile
+++ b/math/blahtexml/Makefile
@@ -1,32 +1,41 @@
 PORTNAME=	blahtexml
 DISTVERSIONPREFIX=	v
 DISTVERSION=	1.0
 CATEGORIES=	math
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	TeX to MathML converter designed with MediaWiki in mind
 WWW=		http://gva.noekeon.org/blahtexml/
 
 LICENSE=	BSD3CLAUSE
 
 LIB_DEPENDS=	libiconv.so:converters/libiconv \
 		libxerces-c.so:textproc/xerces-c3
 
 USES=		gmake localbase:ldflags
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	gvanas
 
 MAKEFILE=	makefile
 MAKE_ARGS=	CFLAGS="${CFLAGS}"
 
 ALL_TARGET=	blahtexml-linux
 
 LDFLAGS+=	-liconv
 
 PLIST_FILES=	bin/${PORTNAME}
 
+.include <bsd.port.options.mk>
+
+.if ${OPSYS} == FreeBSD && ( ${OSVERSION} >= 1400091 || ( ${OSVERSION} >= 1302507 && ${OSVERSION} < 1400000 ))
+USES+=	llvm:max=15
+CC=	clang${LLVM_VERSION}
+CPP=	clang-cpp${LLVM_VERSION}
+CXX=	clang++${LLVM_VERSION}
+.endif
+
 do-install:
 	${INSTALL_PROGRAM} ${WRKSRC}/${PORTNAME} ${STAGEDIR}${PREFIX}/bin
 
 .include <bsd.port.mk>