diff --git a/devel/libcutl/Makefile b/devel/libcutl/Makefile
index 323b2b44feee..bbaad70028c2 100644
--- a/devel/libcutl/Makefile
+++ b/devel/libcutl/Makefile
@@ -1,44 +1,46 @@
 PORTNAME=	libcutl
 PORTVERSION=	1.10.0
 PORTREVISION=	21
 CATEGORIES=	devel
 MASTER_SITES=	https://www.codesynthesis.com/download/${PORTNAME}/${PORTVERSION:R}/
 
 MAINTAINER=	rakuco@FreeBSD.org
 COMMENT=	C++ utility library with generic and independent components
 WWW=		https://www.codesynthesis.com/projects/libcutl/
 
 LICENSE=	MIT
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
 BROKEN_sparc64=	Does not build: cannot configure with boost
 
 LIB_DEPENDS=	libboost_system.so:devel/boost-libs \
 		libexpat.so:textproc/expat2
 
 USES=		compiler:c++11-lib libtool
+# libcutl 1.10.0 is not compatible with C++17, which is the default since clang
+# 16. This means ports depending on it also need to use at most C++14.
 USE_CXXSTD=	c++11
 GNU_CONFIGURE=	yes
 INSTALL_TARGET=	install-strip
 
 # The checks for external boost and external expat are quite limited and do not
 # add the ${LOCALBASE} paths correctly (libboost.m4 uses wrong paths and
 # libexpat.m4 does nothing at all).
 CPPFLAGS+=	-I${LOCALBASE}/include
 LDFLAGS+=	-L${LOCALBASE}/lib
 
 CONFIGURE_ARGS=	--disable-static \
 		--with-boost=${LOCALBASE} \
 		--with-external-boost \
 		--with-external-expat \
 		--with-pkgconfigdir=${PREFIX}/libdata/pkgconfig
 
 OPTIONS_DEFINE=	DOCS
 
 post-patch:
 # Avoid conflict with C++20 <version> by adding .txt suffix
 	@${MV} ${WRKSRC}/version ${WRKSRC}/version.txt
 	@${REINPLACE_CMD} -i .c++20 '/doc_DATA/s/version/&.txt/' \
 		${WRKSRC}/Makefile.in
 
 .include <bsd.port.mk>
diff --git a/devel/xsd/Makefile b/devel/xsd/Makefile
index 06e02ce6f72c..010b73e6e9e4 100644
--- a/devel/xsd/Makefile
+++ b/devel/xsd/Makefile
@@ -1,51 +1,54 @@
 PORTNAME=	xsd
 DISTVERSION=	4.1.0.a11
 PORTREVISION=	1
 DISTVERSIONSUFFIX=	+dep
 CATEGORIES=	devel
 MASTER_SITES=	https://codesynthesis.com/~boris/tmp/${PORTNAME}/${DISTVERSION}/
 
 MAINTAINER=	kde@FreeBSD.org
 COMMENT=	W3C XML Schema to C++ translator
 WWW=		https://www.codesynthesis.com/projects/xsd/
 
 LICENSE=		FLOSSE GPLv2
 LICENSE_COMB=		dual
 LICENSE_NAME_FLOSSE=	FLOSS Exception
 LICENSE_FILE_FLOSSE=	${WRKSRC}/xsd/FLOSSE
 LICENSE_PERMS_FLOSSE=	dist-mirror dist-sell pkg-mirror pkg-sell auto-accept
 
 BUILD_DEPENDS=	${LOCALBASE}/include/build-0.3/abspath.make:devel/build
 # libxsd-frontend should come from a separate port as well, but at the moment
 # its distribution as a separate tarball is so poor that it does not even have
 # a `make install'.
 LIB_DEPENDS=	libcutl.so:devel/libcutl \
 		libxerces-c.so:textproc/xerces-c3
 
 USES=		compiler:c++11-lang ghostscript:build gmake localbase:ldflags tar:bzip2
+# devel/libcutl 1.10.0 does not work with C++17 which is the default since
+# clang 16. This can be removed once that port starts working with C++17 and
+# has its own USE_CXXSTD removed.
 USE_CXXSTD=	c++11
 
 MAKEFILE=	makefile
 MAKE_ARGS=	EXTERNAL_LIBCUTL=y \
 		install_prefix=${STAGEDIR}${PREFIX} \
 		install_man_dir=${STAGEDIR}${MANPREFIX}/man \
 		verbose=1
 ALL_TARGET=	# no default target should be passed to gmake.
 
 OPTIONS_DEFINE=	DOCS EXAMPLES
 
 post-patch:
 # Use devel/build instead of the port's bundled copy.
 	${RM} -r ${WRKSRC}/build-0.3
 	${LN} -s ${LOCALBASE}/include/build-0.3 ${WRKSRC}/build-0.3
 # Avoid conflict with C++20 <version> by adding .txt suffix
 	@${MV} ${WRKSRC}/libxsd-frontend/version \
 		${WRKSRC}/libxsd-frontend/version.txt
 
 post-install:
 # Install examples into the right directory.
 	${MKDIR} ${STAGEDIR}${EXAMPLESDIR}
 	${MV} ${STAGEDIR}${DOCSDIR}/examples/* ${STAGEDIR}${EXAMPLESDIR}
 	${RMDIR} ${STAGEDIR}${DOCSDIR}/examples
 
 .include <bsd.port.mk>