diff --git a/mavutil.py b/mavutil.py
index 28dafb8ea..af4930fcc 100644
--- a/mavutil.py
+++ b/mavutil.py
@@ -1060,6 +1060,7 @@ def __init__(self, filename, planner_format=None,
         self.stop_on_EOF = True
         self._last_message = None
         self._last_timestamp = None
+        self._link = 0
 
     def close(self):
         self.f.close()