Index: head/science/xtb/Makefile
===================================================================
--- head/science/xtb/Makefile	(revision 541204)
+++ head/science/xtb/Makefile	(revision 541205)
@@ -1,22 +1,23 @@
 # Created by: Johannes M Dieterich <jmd@FreeBSD.org>
 # $FreeBSD$
 
 PORTNAME=	xtb
 PORTVERSION=	6.3.2
 DISTVERSIONPREFIX=	v
 CATEGORIES=	science
 
 MAINTAINER=	jmd@FreeBSD.org
 COMMENT=	Semiempirical Extended Tight-Binding Program Package
 
 LICENSE=	GPLv3
 LICENSE_FILE=	${WRKSRC}/COPYING
 
 USES=		fortran cmake blaslapack:openblas
 
 USE_GITHUB=	yes
 GH_ACCOUNT=	grimme-lab
 
 USE_LDCONFIG=	yes
+FFLAGS+=	-std=legacy
 
 .include <bsd.port.mk>