diff --git a/include/u.h b/include/u.h
index 69d14e3..d0cd639 100644
--- a/include/u.h
+++ b/include/u.h
@@ -19,6 +19,7 @@
 #define _BSD_SOURCE 1
 #define _NETBSD_SOURCE 1	/* NetBSD */
 #define _SVID_SOURCE 1
+#define _DEFAULT_SOURCE 1
 #if !defined(__APPLE__) && !defined(__OpenBSD__)
 #	define _XOPEN_SOURCE 1000
 #	define _XOPEN_SOURCE_EXTENDED 1
diff --git a/src/cmd/grap/main.c b/src/cmd/grap/main.c
index db2098f..38c2419 100644
--- a/src/cmd/grap/main.c
+++ b/src/cmd/grap/main.c
@@ -1,4 +1,5 @@
 #define _BSD_SOURCE 1	/* strdup, mkstemp */
+#define _DEFAULT_SOURCE 1
 #include <stdio.h>
 #include <signal.h>
 #include <math.h>
diff --git a/src/cmd/rio/menu.c b/src/cmd/rio/menu.c
index 379291c..dc23f1c 100644
--- a/src/cmd/rio/menu.c
+++ b/src/cmd/rio/menu.c
@@ -4,6 +4,7 @@
 
 /* Copyright (c) 1994-1996 David Hogan, see README for licence details */
 #define _SVID_SOURCE 1	/* putenv in glibc */
+#define _DEFAULT_SOURCE 1
 #include <stdio.h>
 #include <signal.h>
 #include <unistd.h>
diff --git a/src/cmd/troff/n2.c b/src/cmd/troff/n2.c
index 6495d33..2943e55 100644
--- a/src/cmd/troff/n2.c
+++ b/src/cmd/troff/n2.c
@@ -5,6 +5,7 @@
  */
 
 #define _BSD_SOURCE 1	/* popen */
+#define _DEFAULT_SOURCE 1
 #include "tdef.h"
 #include "fns.h"
 #include "ext.h"
diff --git a/src/cmd/troff/n7.c b/src/cmd/troff/n7.c
index 17ab2bd..15bcfd5 100644
--- a/src/cmd/troff/n7.c
+++ b/src/cmd/troff/n7.c
@@ -1,4 +1,5 @@
 #define _BSD_SOURCE 1	/* isascii */
+#define _DEFAULT_SOURCE 1
 #include "tdef.h"
 #include "fns.h"
 #include "ext.h"
diff --git a/src/lib9/utf/utfecpy.c b/src/lib9/utf/utfecpy.c
index cf3535f..bab8136 100644
--- a/src/lib9/utf/utfecpy.c
+++ b/src/lib9/utf/utfecpy.c
@@ -12,6 +12,7 @@
  * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
  */
 #define _BSD_SOURCE 1	/* memccpy */
+#define _DEFAULT_SOURCE 1
 #include <stdarg.h>
 #include <string.h>
 #include "plan9.h"