Ticket #20417: 20417-Server restart needed to load new tags and filters

diff --git a/docs/howto/custom-template-tags.txt b/docs/howto/custom-template-tags.txt
index 0d35654..0c1976c 100644
--- a/docs/howto/custom-template-tags.txt
+++ b/docs/howto/custom-template-tags.txt
@@ -150,6 +150,8 @@ Finally, ``register.filter()`` also accepts three keyword arguments,
 are described in :ref:`filters and auto-escaping <filters-auto-escaping>` and
 :ref:`filters and time zones <filters-timezones>` below.
 
+The webserver must be restarted before a new tag or filter can be used by a template.
+
 Template filters that expect strings
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~