diff --git a/math/fenics-basix/Makefile b/math/fenics-basix/Makefile
index 45ec89302f80..af5890e4c41c 100644
--- a/math/fenics-basix/Makefile
+++ b/math/fenics-basix/Makefile
@@ -1,24 +1,30 @@
 PORTNAME=	fenics-basix
 DISTVERSIONPREFIX=	v
 DISTVERSION=	0.5.0.post0
 CATEGORIES=	math
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	FEniCS finite element basis evaluation library
 
 LICENSE=	MIT
 LICENSE_FILE=	${WRKSRC}/../LICENSE
 
 BUILD_DEPENDS=	xtensor>0:math/xtensor \
 		xtl-quant-stack>0:devel/xtl-quant-stack
 LIB_DEPENDS=	libopenblas.so:math/openblas
 
 USES=		cmake compiler:c++17-lang
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	FEniCS
 GH_PROJECT=	basix
 
 WRKSRC_SUBDIR=	cpp
 
-.include <bsd.port.mk>
+.include <bsd.port.pre.mk>
+
+.if ${CHOSEN_COMPILER_TYPE} == clang && !exists(/usr/include/c++/v1/concepts) # true only on FreeBSD_12
+BROKEN=		system is missing a required C++ feature std::concepts
+.endif
+
+.include <bsd.port.post.mk>