Index: Makefile
===================================================================
--- Makefile	(revision 480103)
+++ Makefile	(working copy)
@@ -14,7 +14,7 @@
 
 IGNORE_FreeBSD_10=	base compiler too old
 
-USES=		cmake:outsource
+USES=		cmake:outsource compiler:c11
 USE_LDCONFIG=	yes
 
 USE_GITHUB=	yes