diff --git a/net-mgmt/fastnetmon/Makefile b/net-mgmt/fastnetmon/Makefile
index 8d00bebb60a0..ebacb752541e 100644
--- a/net-mgmt/fastnetmon/Makefile
+++ b/net-mgmt/fastnetmon/Makefile
@@ -1,71 +1,79 @@
 PORTNAME=	fastnetmon
 PORTVERSION=	1.2.5
 DISTVERSIONPREFIX=	v
 CATEGORIES=	net-mgmt security
 
 MAINTAINER=	farrokhi@FreeBSD.org
 COMMENT=	Very fast DDoS analyzer with sflow/netflow/mirror support
 WWW=		https://fastnetmon.com
 
 LICENSE=	GPLv2
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
 BROKEN_armv6=		does not build: invokes x86 assembler
 BROKEN_armv7=		does not build: invokes x86 assembler
 
 LIB_DEPENDS=	libboost_regex.so:devel/boost-libs \
 		liblog4cpp.so:devel/log4cpp \
 		libmongoc-1.0.so:devel/mongo-c-driver \
 		libjson-c.so:devel/json-c \
 		libbson-1.0.so:devel/libbson \
 		libcapnp.so:devel/capnproto \
 		libgrpc.so:devel/grpc142 \
 		libprotobuf.so:devel/protobuf \
 		libabsl_base.so:devel/abseil \
 		libhiredis.so:databases/hiredis
 
 USES=	cmake compiler:c++11-lang pkgconfig localbase:ldflags ssl
 USE_CXXSTD=	c++14
 USE_GITHUB=	yes
 GH_ACCOUNT=	pavel-odintsov
+USE_RC_SUBR=	${PORTNAME}
+
+CMAKE_ARGS+=	-DENABLE_NETMAP_SUPPORT=ON \
+		-DLINK_WITH_ABSL=ON \
+		-DSET_ABSOLUTE_INSTALL_PATH=OFF \
+		-DCMAKE_INSTALL_MANDIR=${PREFIX}/man
+CMAKE_INSTALL_PREFIX=	${PREFIX}
+CMAKE_SOURCE_PATH=	${WRKSRC}/src
+
+CFLAGS_i386=	-march=i586
+CXXFLAGS += -DBOOST_STACKTRACE_GNU_SOURCE_NOT_REQUIRED \
+	    -D_GNU_SOURCE
 
 USERS=	${PORTNAME}
 GROUPS=	${PORTNAME}
 
-USE_RC_SUBR=	${PORTNAME}
+PORTDOCS=	*
 
 OPTIONS_DEFINE=	DOCS
 
-PORTDOCS=	*
-
-CXXFLAGS += -DBOOST_STACKTRACE_GNU_SOURCE_NOT_REQUIRED \
-	    -D_GNU_SOURCE
-CFLAGS_i386=	-march=i586
-CMAKE_SOURCE_PATH=	${WRKSRC}/src
-CMAKE_ARGS+=	-DENABLE_NETMAP_SUPPORT=ON \
-		-DLINK_WITH_ABSL=ON \
-		-DSET_ABSOLUTE_INSTALL_PATH=OFF \
-		-DCMAKE_INSTALL_MANDIR=${PREFIX}/man
+.include <bsd.port.options.mk>
 
-CMAKE_INSTALL_PREFIX=	${PREFIX}
+.if ${OPSYS} == FreeBSD && ( ${OSVERSION} >= 1400091 || ( ${OSVERSION} >= 1302505 && ${OSVERSION} < 1400000 ))
+USES+=	llvm:max=15
+CC=	clang${LLVM_VERSION}
+CPP=	clang-cpp${LLVM_VERSION}
+CXX=	clang++${LLVM_VERSION}
+.endif
 
 .include <bsd.port.pre.mk>
 
 post-patch:
 	@${REINPLACE_CMD} -e 's|/usr/local|${PREFIX}|; \
 		s|/var/run|&/fastnetmon|g; s|/var/log|&/fastnetmon|g; \
 		s|"/etc/|"${PREFIX}/etc/|g; s|/root/fastnetmon|${DATADIR}|g' \
 		${WRKSRC}/src/fastnetmon.conf ${WRKSRC}/src/fastnetmon.cpp
 	@${REINPLACE_CMD} -e 's|%%PREFIX%%|${PREFIX}|g' \
 		${WRKSRC}/src/man/fastnetmon.8
 
 post-install:
 	${MV} ${STAGEDIR}${PREFIX}/etc/${PORTNAME}.conf \
 		${STAGEDIR}${PREFIX}/etc/${PORTNAME}.conf.sample
 	${MKDIR} ${STAGEDIR}/var/run/fastnetmon ${STAGEDIR}/var/log/fastnetmon_attacks
 	${INSTALL_SCRIPT} ${WRKSRC}/src/notify_about_attack.sh ${STAGEDIR}${PREFIX}/bin
 
 post-install-DOCS-on:
 	cd ${WRKSRC} && ${COPYTREE_SHARE} "README.md docs" ${STAGEDIR}${DOCSDIR}
 
 .include <bsd.port.post.mk>