Index: head/math/pynac/Makefile
===================================================================
--- head/math/pynac/Makefile	(revision 532262)
+++ head/math/pynac/Makefile	(revision 532263)
@@ -1,33 +1,43 @@
 # Created by: thierry@pompo.net
 # $FreeBSD$
 
 PORTNAME=	pynac
 PORTVERSION=	0.7.26
+PORTREVISION=	1
 CATEGORIES=	math python
 MASTER_SITES=	https://github.com/${PORTNAME}/${PORTNAME}/releases/download/${DISTNAME}/
 
 MAINTAINER=	thierry@FreeBSD.org
 COMMENT=	Symbolic computation with Python objects, Sage Math support library
 
 LICENSE=	GPLv2
 
 LIB_DEPENDS=	libgmp.so:math/gmp		\
 		libntl.so:math/ntl		\
 		libflint.so:math/flint2		\
 		libSingular.so:math/singular
 
 USES=		compiler:c++11-lang libtool localbase pkgconfig python:3.6+ tar:bz2
 
 OPTIONS_DEFINE=		GIAC
-OPTIONS_DEFAULT=	GIAC
+OPTIONS_DEFAULT=
 GIAC_DESC=		Use giac for polynomial manipulations
 GIAC_LIB_DEPENDS=	libgiac.so:math/giacxcas
 GIAC_CONFIGURE_ON=	--with-giac
 GIAC_CONFIGURE_OFF=	--without-giac
 GIAC_LIBS=		"-lm"
 
 GNU_CONFIGURE=	yes
 USE_LDCONFIG=	yes
 TEST_TARGET=	check
+
+pre-configure-GIAC-on:
+	${REINPLACE_CMD} -e 's|-lpynac|-lpynac -lgiac|' ${WRKSRC}/pynac.pc.in
+
+.include <bsd.port.options.mk>
+
+.if ${PORT_OPTIONS:MGIAC}
+BROKEN_FreeBSD_11=	libgiac is broken (undefined reference to `__divmodti4@GCC_7.0.0')
+.endif
 
 .include <bsd.port.mk>