https://bugzilla.redhat.com/show_bug.cgi?id=1644317
diff --git a/ax25ipd/io.c b/ax25ipd/io.c
index a31cc7d..26f0be7 100644
--- a/ax25ipd/io.c
+++ b/ax25ipd/io.c
@@ -11,6 +11,10 @@
#undef USE_ICMP /* not implemented yet, sorry */
+/* For ptsname */
+#define _DEFAULT_SOURCE
+#define _XOPEN_SOURCE 500
+
#include "ax25ipd.h"
#include <sys/types.h>