diff --git a/plugins/TwitterBridge/Notice_to_status.php b/plugins/TwitterBridge/Notice_to_status.php
index 2e32ba963c..3b8f816cfc 100644
--- a/plugins/TwitterBridge/Notice_to_status.php
+++ b/plugins/TwitterBridge/Notice_to_status.php
@@ -144,6 +144,7 @@ class Notice_to_status extends Memcached_DataObject
 
     /**
      * Save a mapping between a notice and a status
+     * Warning: status_id values may not fit in 32-bit integers.
      *
      * @param integer $notice_id ID of the notice in StatusNet
      * @param integer $status_id ID of the status in Twitter
@@ -153,12 +154,18 @@ class Notice_to_status extends Memcached_DataObject
 
     static function saveNew($notice_id, $status_id)
     {
+        if (empty($notice_id)) {
+            throw new Exception("Invalid notice_id $notice_id");
+        }
         $n2s = Notice_to_status::staticGet('notice_id', $notice_id);
 
         if (!empty($n2s)) {
             return $n2s;
         }
 
+        if (empty($status_id)) {
+            throw new Exception("Invalid status_id $status_id");
+        }
         $n2s = Notice_to_status::staticGet('status_id', $status_id);
 
         if (!empty($n2s)) {
diff --git a/plugins/TwitterBridge/twitter.php b/plugins/TwitterBridge/twitter.php
index cd1ad70b9b..b34488069a 100644
--- a/plugins/TwitterBridge/twitter.php
+++ b/plugins/TwitterBridge/twitter.php
@@ -128,6 +128,16 @@ function is_twitter_notice($id)
     return (!empty($n2s));
 }
 
+/**
+ * Check if we need to broadcast a notice over the Twitter bridge, and
+ * do so if necessary. Will determine whether to do a straight post or
+ * a repeat/retweet
+ *
+ * This function is meant to be called directly from TwitterQueueHandler.
+ *
+ * @param Notice $notice
+ * @return boolean true if complete or successful, false if we should retry
+ */
 function broadcast_twitter($notice)
 {
     $flink = Foreign_link::getByUserID($notice->profile_id,
@@ -137,8 +147,13 @@ function broadcast_twitter($notice)
     if (!empty($flink) && TwitterOAuthClient::isPackedToken($flink->credentials)) {
         if (!empty($notice->repeat_of) && is_twitter_notice($notice->repeat_of)) {
             $retweet = retweet_notice($flink, Notice::staticGet('id', $notice->repeat_of));
-            if (!empty($retweet)) {
+            if (is_object($retweet)) {
                 Notice_to_status::saveNew($notice->id, $retweet->id);
+                return true;
+            } else {
+                // Our error processing will have decided if we need to requeue
+                // this or can discard safely.
+                return $retweet;
             }
         } else if (is_twitter_bound($notice, $flink)) {
             return broadcast_oauth($notice, $flink);
@@ -148,6 +163,21 @@ function broadcast_twitter($notice)
     return true;
 }
 
+/**
+ * Send a retweet to Twitter for a notice that has been previously bridged
+ * in or out.
+ *
+ * Warning: the return value is not guaranteed to be an object; some error
+ * conditions will return a 'true' which should be passed on to a calling
+ * queue handler.
+ *
+ * No local information about the resulting retweet is saved: it's up to
+ * caller to save new mappings etc if appropriate.
+ *
+ * @param Foreign_link $flink
+ * @param Notice $notice
+ * @return mixed object with resulting Twitter status data on success, or true/false/null on error conditions.
+ */
 function retweet_notice($flink, $notice)
 {
     $token = TwitterOAuthClient::unpackToken($flink->credentials);