diff --git a/math/blahtexml/Makefile b/math/blahtexml/Makefile
index f86f51ff37ec4..3619a4cf7b1af 100644
--- a/math/blahtexml/Makefile
+++ b/math/blahtexml/Makefile
@@ -26,6 +26,15 @@ 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