diff --git a/plugins/senderbase/senderbase b/plugins/senderbase/senderbase
index d00f5d18..99d404cb 100755
--- a/plugins/senderbase/senderbase
+++ b/plugins/senderbase/senderbase
@@ -19,6 +19,12 @@ variable to the appropriate value.
 
 Phil! Gold <phil_g@pobox.com>
 
+=head1 LICENSE
+
+This plugin is made available under a CC0 waiver:
+
+  https://creativecommons.org/publicdomain/zero/1.0/
+
 =head1 MAGIC MARKERS
 
  #%# family=auto