Index: head/math/poly2tri/Makefile
===================================================================
--- head/math/poly2tri/Makefile	(revision 525136)
+++ head/math/poly2tri/Makefile	(revision 525137)
@@ -1,26 +1,26 @@
 # $FreeBSD$
 
 PORTNAME=	poly2tri
 DISTVERSION=	g20191130
 CATEGORIES=	math
 
 MAINTAINER=	yuri@FreeBSD.org
 COMMENT=	2D constrained Delaunay triangulation library
 
 LICENSE=	BSD3CLAUSE
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
 LIB_DEPENDS=	libglfw.so:graphics/glfw
 
-USES=		gl localbase:ldflags waf
+USES=		compiler:c11 gl localbase:ldflags waf
 USE_GITHUB=	yes
 GH_ACCOUNT=	jhasse
 GH_TAGNAME=	e6e63dd29ef0805b3e40fe1832c2f1fe2307943a
 USE_GL=		gl
 
 PLIST_FILES=	bin/p2t
 
 post-stage:
 	@${STRIP_CMD} ${STAGEDIR}${PREFIX}/bin/p2t
 
 .include <bsd.port.mk>