Index: head/devel/kf5-kservice/Makefile
===================================================================
--- head/devel/kf5-kservice/Makefile	(revision 426542)
+++ head/devel/kf5-kservice/Makefile	(revision 426543)
@@ -1,16 +1,22 @@
 # Created by: tcberner
 # $FreeBSD$
 
 PORTNAME=	kservice
 PORTVERSION=	${KDE_FRAMEWORKS_VERSION}
 CATEGORIES=	devel kde kde-frameworks
 
 MAINTAINER=	kde@FreeBSD.org
 COMMENT=	KF5 advanced plugin and service introspection
 
 USES=		bison cmake:outsource compiler:c++11-lib gettext kde:5 tar:xz
 USE_KDE=	archive config coreaddons crash dbusaddons \
 		doctools ecm i18n
 USE_QT5=	buildtools_build core dbus gui qmake_build xml
 
-.include <bsd.port.mk>
+.include <bsd.port.pre.mk>
+# Flex on FreeBSD 9 and older 10 is too old
+.if ${OPSYS} == FreeBSD && ${OSVERSION} < 1000033
+BUILD_DEPENDS+=	${LOCALBASE}/bin/flex:textproc/flex
+.endif
+
+.include <bsd.port.post.mk>
Index: head/devel/kf5-solid/Makefile
===================================================================
--- head/devel/kf5-solid/Makefile	(revision 426542)
+++ head/devel/kf5-solid/Makefile	(revision 426543)
@@ -1,16 +1,22 @@
 # Created by: tcberner
 # $FreeBSD$
 
 PORTNAME=	solid
 PORTVERSION=	${KDE_FRAMEWORKS_VERSION}
 CATEGORIES=	devel kde kde-frameworks
 
 MAINTAINER=	kde@FreeBSD.org
 COMMENT=	KF5 hardware integration and detection
 
 USES=		bison cmake:outsource compiler:c++11-lib kde:5 tar:xz
 USE_KDE=	ecm
 USE_QT5=	buildtools_build concurrent core dbus gui linguisttools \
 		network qmake_build qml testlib widgets xml
 
-.include <bsd.port.mk>
+.include <bsd.port.pre.mk>
+# Flex on FreeBSD 9 and older 10 is too old
+.if ${OPSYS} == FreeBSD && ${OSVERSION} < 1000033
+BUILD_DEPENDS+=	${LOCALBASE}/bin/flex:textproc/flex
+.endif
+
+.include <bsd.port.post.mk>