Help with Shimano reel?

My Shimano Navi is starting to lay line to the front of the spool? What's wrong? How can I fix it?

Remove spool and fit small washer/washers on spool spindle. There should already be a fibre washer on the spindle. Refit spool which should now be sitting slightly further forward. Reel some line on and check lay.

Thanks, I'll give that a shot.