diff --git a/contrib/libcxxrt/guard.cc b/contrib/libcxxrt/guard.cc
index f1c4c69fa6b9..34d294cf7432 100644
--- a/contrib/libcxxrt/guard.cc
+++ b/contrib/libcxxrt/guard.cc
@@ -101,7 +101,7 @@ typedef struct {
 	uint32_t init_half;
 	uint32_t lock_half;
 } guard_t;
-_Static_assert(sizeof(guard_t) == sizeof(uint64_t), "");
+static_assert(sizeof(guard_t) == sizeof(uint64_t), "");
 static const uint32_t LOCKED = 1;
 static const uint32_t INITIALISED = static_cast<guard_lock_t>(1) << 24;
 #	endif
diff --git a/lib/libcxxrt/Makefile b/lib/libcxxrt/Makefile
index d197361a9a66..b580618b8fee 100644
--- a/lib/libcxxrt/Makefile
+++ b/lib/libcxxrt/Makefile
@@ -20,7 +20,10 @@ SRCS+=		libelftc_dem_gnu3.c\
 		guard.cc
 
 WARNS=		0
-CFLAGS+=	-I${SRCDIR}
+CFLAGS+=	-I${SRCDIR} -nostdinc++
+.if empty(CXXFLAGS:M-std=*)
+CXXFLAGS+=	-std=c++11
+.endif
 VERSION_MAP=	${.CURDIR}/Version.map
 
 .include <bsd.lib.mk>