diff --git a/mk/os-Linux.mk b/mk/os-Linux.mk
index bb6fa372..60235b8d 100644
--- a/mk/os-Linux.mk
+++ b/mk/os-Linux.mk
@@ -4,7 +4,7 @@
 SFX=		.Linux.in
 PKG_PREFIX?=	/usr
 
-CPPFLAGS+=	-D_BSD_SOURCE -D_XOPEN_SOURCE=700
+CPPFLAGS+=	-D_BSD_SOURCE -D_DEFAULT_SOURCE -D_XOPEN_SOURCE=700
 LIBDL=		-Wl,-Bdynamic -ldl
 
 ifeq (${MKSELINUX},yes)