--- Makefile	(revision 486250)
+++ Makefile	(working copy)
@@ -21,7 +21,7 @@ 
 
 CONFLICTS_BUILD=	Ipopt
 
-USES=		cmake:outsource readline tar:tgz
+USES=		compiler:c11 cmake:outsource readline tar:tgz
 EXTRACT_CMD=	gtar
 USE_LDCONFIG=	yes
 PLIST_SUB=	SHL4=${DISTVERSION}.0 SHL2=${DISTVERSION:R}