1 files changed, 4 insertions, 0 deletions
diff --git a/gpsmon.c b/gpsmon.c
index f9475887..ea0991be 100644
--- a/gpsmon.c
+++ b/gpsmon.c
@@ -4,6 +4,10 @@
  * This file is Copyright (c) 2010 by the GPSD project
  * BSD terms apply: see the file COPYING in the distribution root for details.
  */
+
+/* for vsnprintf() FreeBSD wants __ISO_C_VISIBLE >= 1999 */
+#define __ISO_C_VISIBLE 1999
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdbool.h>