diff --git a/classes/Managed_DataObject.php b/classes/Managed_DataObject.php
index 7263b3e320..552d980fba 100644
--- a/classes/Managed_DataObject.php
+++ b/classes/Managed_DataObject.php
@@ -152,4 +152,18 @@ abstract class Managed_DataObject extends Memcached_DataObject
 
         return $style;
     }
+
+    function links()
+    {
+        $links = array();
+
+        $table = call_user_func(array(get_class($this), 'schemaDef'));
+
+        foreach ($table['foreign keys'] as $keyname => $keydef) {
+            if (count($keydef) == 2 && is_string($keydef[0]) && is_array($keydef[1]) && count($keydef[1]) == 1) {
+                $links[$keydef[1][0]] = $keydef[0].':'.$keydef[1][1];
+            }
+        }
+        return $links;
+    }
 }
\ No newline at end of file
diff --git a/classes/Profile.php b/classes/Profile.php
index bcbb406ae0..228a0ae202 100644
--- a/classes/Profile.php
+++ b/classes/Profile.php
@@ -435,6 +435,7 @@ class Profile extends Managed_DataObject
         $tags->tagged = $this->id;
 
         $lists->joinAdd($tags);
+
         #@fixme: postgres (round(date_part('epoch', my_date)))
         $lists->selectAdd('unix_timestamp(profile_tag.modified) as "cursor"');
 
@@ -507,7 +508,8 @@ class Profile extends Managed_DataObject
         $lists = new Profile_list();
         $subs = new Profile_tag_subscription();
 
-        $lists->joinAdd($subs);
+        $lists->joinAdd('id', 'profile_tag_subscription:profile_tag_id');
+
         #@fixme: postgres (round(date_part('epoch', my_date)))
         $lists->selectAdd('unix_timestamp(profile_tag_subscription.created) as "cursor"');
 
diff --git a/classes/Profile_list.php b/classes/Profile_list.php
index 50aa71f55d..c433a53fee 100644
--- a/classes/Profile_list.php
+++ b/classes/Profile_list.php
@@ -220,10 +220,9 @@ class Profile_list extends Managed_DataObject
     function getSubscribers($offset=0, $limit=null, $since=0, $upto=0)
     {
         $subs = new Profile();
-        $sub = new Profile_tag_subscription();
-        $sub->profile_tag_id = $this->id;
 
-        $subs->joinAdd($sub);
+        $subs->joinAdd(array('id', 'profile_tag_subscription:profile_tag_id'));
+
         $subs->selectAdd('unix_timestamp(profile_tag_subscription.' .
                          'created) as "cursor"');
 
diff --git a/lib/default.php b/lib/default.php
index 9c4c8cab05..71b2257cd5 100644
--- a/lib/default.php
+++ b/lib/default.php
@@ -310,7 +310,8 @@ $default =
                                  'TagSub' => null,
                                  'OpenID' => null,
                                  'Directory' => null,
-                                 'ExtendedProfile' => null),
+                                 'ExtendedProfile' => null,
+                                 'Activity' => null),
               'locale_path' => false, // Set to a path to use *instead of* each plugin's own locale subdirectories
               'server' => null,
               'sslserver' => null,
diff --git a/lib/peopletagnoticestream.php b/lib/peopletagnoticestream.php
index 9477ca8ea6..e82d754e8d 100644
--- a/lib/peopletagnoticestream.php
+++ b/lib/peopletagnoticestream.php
@@ -96,10 +96,10 @@ class RawPeopletagNoticeStream extends NoticeStream
         $notice->selectAdd();
         $notice->selectAdd('notice.id');
 
-        $ptag = new Profile_tag();
-        $ptag->tag    = $this->profile_list->tag;
-        $ptag->tagger = $this->profile_list->tagger;
-        $notice->joinAdd($ptag);
+        $notice->joinAdd(array('profile_id', 'profile_tag:tagged'));
+
+        $notice->whereAdd(sprintf('profile_tag.tag = "%s"', $this->profile_list->tag));
+        $notice->whereAdd(sprintf('profile_tag.tagger = %d', $this->profile_list->tagger));
 
         if ($since_id != 0) {
             $notice->whereAdd('notice.id > ' . $since_id);