diff --git a/gnu/lib/libstdc++/Makefile b/gnu/lib/libstdc++/Makefile
index d19f9f3bb3ff..fa1d67e7ce64 100644
--- a/gnu/lib/libstdc++/Makefile
+++ b/gnu/lib/libstdc++/Makefile
@@ -632,9 +632,9 @@ ${VERSION_MAP}: ${SRCDIR}/config/abi/pre/gnu.ver
 
 CLEANFILES+=	${VERSION_MAP}
 
+CXXFLAGS.clang+= -stdlib=libstdc++
+
 .include <bsd.lib.mk>
 
 # Filter out libc++-specific flags, and -std= flags above c++98 or gnu++98.
 CXXFLAGS:=	${CXXFLAGS:N-stdlib=libc++:N-std=c++[01][13x]:N-std=gnu++[01][13x]}
-
-CXXFLAGS.clang+= -stdlib=libstdc++
diff --git a/gnu/lib/libsupc++/Makefile b/gnu/lib/libsupc++/Makefile
index 5cc5f04adf67..c7cc30e53787 100644
--- a/gnu/lib/libsupc++/Makefile
+++ b/gnu/lib/libsupc++/Makefile
@@ -51,10 +51,9 @@ CLEANFILES+=	unwind.h
 
 VERSION_MAP=	${.CURDIR}/Version.map
 
+CXXFLAGS.clang+= -stdlib=libstdc++
 
 .include <bsd.lib.mk>
 
 # Filter out libc++-specific flags, and -std= flags above c++98 or gnu++98.
 CXXFLAGS:=	${CXXFLAGS:N-stdlib=libc++:N-std=c++[01][13x]:N-std=gnu++[01][13x]}
-
-CXXFLAGS.clang+= -stdlib=libstdc++