diff --git a/gnu/lib/libstdc++/Makefile b/gnu/lib/libstdc++/Makefile
index c3734429db0..14bb04191f1 100644
--- a/gnu/lib/libstdc++/Makefile
+++ b/gnu/lib/libstdc++/Makefile
@@ -22,6 +22,7 @@ CFLAGS+=	-I${GCCLIB}/include -I${SRCDIR}/include -I.
 CFLAGS+=	-frandom-seed=RepeatabilityConsideredGood
 CXXFLAGS+=	-fno-implicit-templates -ffunction-sections -fdata-sections \
 		-Wno-deprecated
+CXXFLAGS:=	${CXXFLAGS:N-stdlib=libc++:N-std=c++[01][13x]:N-std=gnu++[01][13x]}
 PO_CXXFLAGS=	${CXXFLAGS:N-ffunction-sections}
 
 DPADD=		${LIBM}
diff --git a/gnu/lib/libsupc++/Makefile b/gnu/lib/libsupc++/Makefile
index a6519897053..76fa1018cab 100644
--- a/gnu/lib/libsupc++/Makefile
+++ b/gnu/lib/libsupc++/Makefile
@@ -24,6 +24,7 @@ CFLAGS+=	-I${GCCLIB}/include -I${SRCDIR} -I${GCCDIR}
 CFLAGS+=	-I${.CURDIR}/../libstdc++ -I.
 CFLAGS+=	-frandom-seed=RepeatabilityConsideredGood
 CXXFLAGS+=	-fno-implicit-templates -ffunction-sections -fdata-sections
+CXXFLAGS:=	${CXXFLAGS:N-stdlib=libc++:N-std=c++[01][13x]:N-std=gnu++[01][13x]}
 PO_CXXFLAGS=    ${CXXFLAGS:N-ffunction-sections}
 
 HDRS=	exception new typeinfo cxxabi.h exception_defines.h