diff --git a/stbt_rig.py b/stbt_rig.py
index bb7adb7..acbbe0f 100755
--- a/stbt_rig.py
+++ b/stbt_rig.py
@@ -1707,7 +1707,7 @@ def flock(filename):
     def file_lock(fileno):
         # Arbitrarily chosen position in the file, sufficiently far from the
         # beginning that it won't overlap with the pid:
-        LOCK_POS = 20
+        LOCK_POS = 4096
 
         import msvcrt  # pylint: disable=import-error
         # Seek to specific position and lock 1 byte.  We don't want to lock the