diff --git a/mail/libdkim/Makefile b/mail/libdkim/Makefile
--- a/mail/libdkim/Makefile
+++ b/mail/libdkim/Makefile
@@ -10,7 +10,7 @@
 LICENSE=	APACHE20
 
 USES=		uidfix zip ssl
-CXXFLAGS+=	-std=gnu++98
+USE_CXXSTD=	gnu++98
 USE_LDCONFIG=	YES
 SHLIB_MAJOR=	1
 PLIST_SUB=	SHLIB_MAJOR="${SHLIB_MAJOR}"