diff --git a/doc/upgrading.txt b/doc/upgrading.txt
index fdcfcd5f..c22e7bf1 100644
--- a/doc/upgrading.txt
+++ b/doc/upgrading.txt
@@ -8,6 +8,9 @@ the output format will change.
 For example existing SQL tables can be altered with:
 alter table linkcheck add (modified varchar(256));
 
+The default User-Agent string used by LinkChecker is now
+Mozilla/5.0 (compatible; LinkChecker/8.1; +http://linkchecker.sourceforge.net/)
+
 Migrating from 7.9 to 8.0
 -------------------------
 Python 2.7.2 or newer is required (Python 3.x is not supported though).