diff --git a/docs/changelog/7.x.x.txt b/docs/changelog/7.x.x.txt
index f265b1297..5f03debcb 100644
--- a/docs/changelog/7.x.x.txt
+++ b/docs/changelog/7.x.x.txt
@@ -14,6 +14,7 @@
  - added FilePump, a way to reduce Yslow scores by minimizing JS, CSS and the number of files transferred.
  - fixed #10394: CC Purchases Fail When Variants Contain Trailing Zero(s)
  - fixed #10332: Matrix: last updated fields = today
+ - fixed Thread subscription groups not cleaned up during purge.
 
 7.7.6
  - Added mobile style template.  If enabled in settings, will serve alternate style templates
diff --git a/lib/WebGUI/Asset/Post/Thread.pm b/lib/WebGUI/Asset/Post/Thread.pm
index cee9574c0..5780f238a 100644
--- a/lib/WebGUI/Asset/Post/Thread.pm
+++ b/lib/WebGUI/Asset/Post/Thread.pm
@@ -602,10 +602,22 @@ sub processPropertiesFromFormPost {
 }
 
 #-------------------------------------------------------------------
+
+=head2 purge
+
+Extend the base class to delete from the Thread_read table, and to delete
+the subscriptionGroup for this thread.
+
+=cut
+
 sub purge {
-	my $self = shift;
-	$self->session->db->write("delete from Thread_read where threadId=?",[$self->getId]);
-        $self->SUPER::purge;
+    my $self = shift;
+    $self->session->db->write("delete from Thread_read where threadId=?",[$self->getId]);
+    my $group = WebGUI::Group->new($self->session, $self->get("subscriptionGroupId"));
+    if ($group) {
+        $group->delete;
+    }
+    $self->SUPER::purge;
 }
 
 #-------------------------------------------------------------------