diff --git a/cad/klayout/Makefile b/cad/klayout/Makefile
index ef8869016fec..3c3b860e4ea2 100644
--- a/cad/klayout/Makefile
+++ b/cad/klayout/Makefile
@@ -1,84 +1,84 @@
 PORTNAME=	klayout
 PORTVERSION=	0.27.3
 PORTREVISION=	1
 DISTVERSIONPREFIX=	v
 CATEGORIES=	cad
 
 MAINTAINER=	hrs@FreeBSD.org
 COMMENT=	Qt-based chip mask layout viewing and editing tool
 
 LICENSE=	GPLv2
 
 BROKEN_i386=	type 'hash<long long>' does not provide a call operator
 BROKEN_powerpc=	type 'hash<long long>' does not provide a call operator
 BROKEN_sparc64=	Does not compile on sparc64: gcc bug
 
 USES=		compiler:c++0x gmake gl python qt:5
 USE_GITHUB=	yes
 GH_ACCOUNT=	KLayout
 USE_GL=		gl
 USE_RUBY=	yes
 USE_QT=		core buildtools designer gui multimedia network printsupport \
 		qmake sql svg testlib uitools widgets xml xmlpatterns
 USE_LDCONFIG=	yes
 
-CXXFLAGS+=	-fPIC -I${LOCALBASE}/include/qt5 \
+CXXFLAGS+=	-fdeclspec -fPIC -I${LOCALBASE}/include/qt5 \
 		${QT5MODULES:S,^,-I${LOCALBASE}/include/qt5/Qt,}
 LDFLAGS+=	${LIBS} ${QT5MODULES:S,^,-lQt5,} \
 		-L${LOCALBASE}/lib/qt5 -lpthread
 LDFLAGS+=	-L${BUILD_WRKSRC} # workaround for the error: unable to find library -lklayout_lib: https://github.com/KLayout/klayout/issues/955
 QT5MODULES=	Core Designer Gui Multimedia MultimediaWidgets \
 		Network PrintSupport Sql Svg Test Widgets Xml XmlPatterns
 MAKE_ENV=	INSTALLROOT=${STAGEDIR} \
 		PYTHON_SITELIBDIR=${PYTHON_SITELIBDIR}
 BUILD_WRKSRC=	${WRKSRC}/build-release
 INSTALL_WRKSRC=	${WRKSRC}/build-release
 TEST_WRKSRC=	${WRKSRC}/build-release
 
 do-configure:
 	cd ${WRKSRC} && \
 	    ${SETENV} ${MAKE_ENV} ${SH} build.sh \
 		-with-qtbinding \
 		-qt5 \
 		-rpath "${PREFIX}/lib/klayout" \
 		-prefix "${PREFIX}" \
 		-python ${PYTHON_CMD} \
 		-ruby ${RUBY} \
 		-dry-run
 
 post-configure:
 	${ECHO_CMD} "#define PLUGINS_BASEDIR \"${PREFIX}/lib/klayout\"" \
 	    > ${WRKSRC}/src/lay/lay/laySystemPathsDefaults.h
 
 pre-install:
 	for D in lib db tl rdb pya; do \
 	    ${MKDIR} ${STAGEDIR}${PYTHON_SITELIBDIR}/klayout/$${D}; \
 	done
 	for D in db_plugins lay_plugins; do \
 	    ${MKDIR} ${STAGEDIR}${PREFIX}/lib/klayout/$${D}; \
 	done
 
 post-install:
 	cd ${INSTALL_WRKSRC} && \
 	    ${STRIP_CMD} `${FIND} libklayout*so* -type f` && \
 	    ${MV} libklayout*so* ${STAGEDIR}${PREFIX}/lib/klayout
 .for D in db_plugins lay_plugins
 	cd ${INSTALL_WRKSRC}/$D && \
 	    ${STRIP_CMD} `${FIND} *so* -type f` && \
 	    ${MV} *so* ${STAGEDIR}${PREFIX}/lib/klayout/$D
 .endfor
 	cd ${INSTALL_WRKSRC}/pymod && \
 	    ${STRIP_CMD} `${FIND} lib*so* -type f` && \
 	    ${MV} lib*so* ${STAGEDIR}${PREFIX}/lib/klayout
 	cd ${STAGEDIR}${PYTHON_SITELIBDIR}/klayout && \
 	    ${STRIP_CMD} `${FIND} *.so -type f`
 	cd ${INSTALL_WRKSRC} && \
 	    ${INSTALL_PROGRAM} klayout strm* ${STAGEDIR}${PREFIX}/bin
 
 do-test:
 	cd ${TEST_WRKSRC} && \
 	    ${SETENV} QT_QPA_PLATFORM=offscreen TESTTMP=testtmp TESTSRC=.. \
 	    LD_LIBRARY_PATH=${STAGEDIR}${PREFIX}/lib/klayout/db_plugins:${STAGEDIR}${PREFIX}/lib/klayout/lay_plugins \
 	    ./ut_runner
 
 .include <bsd.port.mk>