Index: head/lang/retro12/Makefile
===================================================================
--- head/lang/retro12/Makefile	(revision 516776)
+++ head/lang/retro12/Makefile	(revision 516777)
@@ -1,49 +1,50 @@
 # $FreeBSD$
 
 PORTNAME=	retro12
 DISTVERSION=	2019.10
 CATEGORIES=	lang
 MASTER_SITES=	http://forthworks.com/retro/r/ \
 		https://forthworks.com/retro/r/
 DISTNAME=	${PORTNAME:tu}-${DISTVERSION}
 
 MAINTAINER=	0mp@FreeBSD.org
 COMMENT=	Clean, elegant, and pragmatic dialect of Forth
 
 LICENSE=	ISCL
 LICENSE_FILE=	${WRKSRC}/LICENSE
 
 USES=		ncurses shebangfix
+USE_CSTD=	c99
 
 SHEBANG_FILES=	example/Atua*
 SHEBANG_LANG=	retro
 
 MAKE_ENV=	DATADIR=${DATADIR} \
 		DESTDIR=${DESTDIR} \
 		DOCSDIR=${DOCSDIR} \
 		EXAMPLESDIR=${EXAMPLESDIR} \
 		PREFIX=${PREFIX}
 # There are race conditions in the makefile due to missing dependencies for
 # targets as upstream tests releases on single core machines.
 MAKE_JOBS_UNSAFE=	yes
 INSTALL_TARGET=	install-strip
 TEST_TARGET=	test
 
 PLIST_FILES=	bin/retro \
 		bin/retro-describe \
 		bin/retro-document \
 		bin/retro-embedimage \
 		bin/retro-extend \
 		bin/retro-muri \
 		bin/retro-tags \
 		bin/retro-unu
 
 PORTDATA=	glossary.retro ngaImage tests words.tsv
 
 PORTDOCS=	README RELEASE-NOTES doc
 
 PORTEXAMPLES=	example
 
 OPTIONS_DEFINE=	DOCS EXAMPLES
 
 .include <bsd.port.mk>