diff --git a/lib/threadingnoticestream.php b/lib/threadingnoticestream.php
new file mode 100644
index 0000000000..c4b35f4092
--- /dev/null
+++ b/lib/threadingnoticestream.php
@@ -0,0 +1,70 @@
+<?php
+/**
+ * StatusNet - the distributed open-source microblogging tool
+ * Copyright (C) 2011, StatusNet, Inc.
+ *
+ * Notice stream that's good for threading lists
+ * 
+ * PHP version 5
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * @category  Notice stream
+ * @package   StatusNet
+ * @author    Evan Prodromou <evan@status.net>
+ * @copyright 2011 StatusNet, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
+ * @link      http://status.net/
+ */
+
+if (!defined('STATUSNET')) {
+    // This check helps protect against security problems;
+    // your code file can't be executed directly from the web.
+    exit(1);
+}
+
+/**
+ * This notice stream filters notices by whether their conversation
+ * has been seen before. It's a good (well, OK) way to get streams
+ * for a ThreadedNoticeList display.
+ *
+ * @category  Notice stream
+ * @package   StatusNet
+ * @author    Evan Prodromou <evan@status.net>
+ * @copyright 2011 StatusNet, Inc.
+ * @license   http://www.fsf.org/licensing/licenses/agpl-3.0.html AGPL 3.0
+ * @link      http://status.net/
+ */
+
+class ThreadingNoticeStream extends FilteringNoticeStream
+{
+    protected $seen = array();
+
+    function getNotices($offset, $limit, $sinceId=null, $maxId=null)
+    {
+        // Clear this each time we're called
+        $this->seen = array();
+        return parent::getNotices($offset, $limit, $sinceId, $maxId);
+    }
+
+    function filter($notice)
+    {
+        if (!array_key_exists($notice->id, $this->seen)) {
+            $this->seen[$notice->id] = true;
+            return true;
+        } else {
+            return false;
+        }
+    }
+}