diff --git a/defaults.ini b/defaults.ini
index 4068660..b179f8e 100644
--- a/defaults.ini
+++ b/defaults.ini
@@ -1278,6 +1278,9 @@ extra_valid_entries:size,universe,universeUrl,universeHTML,sitetags,notice,codes
 #extra_titlepage_entries:size,universeHTML,sitetags,notice
 include_in_codes:sitetags
 
+## adds to include_subject_tags instead of replacing it.
+#extra_subject_tags:sitetags
+
 size_label:Size
 universe_label:Universe
 universeUrl_label:Universe URL
diff --git a/plugin-defaults.ini b/plugin-defaults.ini
index b45c528..e440d11 100644
--- a/plugin-defaults.ini
+++ b/plugin-defaults.ini
@@ -1272,6 +1272,9 @@ extra_valid_entries:size,universe,universeUrl,universeHTML,sitetags,notice,codes
 #extra_titlepage_entries:size,universeHTML,sitetags,notice
 include_in_codes:sitetags
 
+## adds to include_subject_tags instead of replacing it.
+#extra_subject_tags:sitetags
+
 size_label:Size
 universe_label:Universe
 universeUrl_label:Universe URL