diff --git a/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Base.php b/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Base.php
index 19978c1b971..0585f2f9065 100644
--- a/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Base.php
+++ b/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Base.php
@@ -86,12 +86,13 @@ public function setLogger(Horde_Log_Logger $logger)
     }
 
     /**
-     * Synchronize the preferences information with the information from the
-     * backend.
+     * Synchronize any changes with the History driver.
      *
      * @param array $params Additional parameters:
      *   - changes: (array)  An array of arrays keyed by backend id containing
-     *                       information about each change.
+     *                       information about each change. If not present,
+     *                       triggers a full history sync.
+     *   - is_reset: (boolean)  If true, indicates that UIDVALIDITY changed.
      */
     public function synchronize($params = array())
     {
@@ -112,7 +113,6 @@ public function synchronize($params = array())
                 if (empty($prefix)) {
                     return;
                 }
-
                 $this->_logger->debug(sprintf(
                     'History: Incremental update for user: %s, folder: %s, prefix: %s',
                     $user, $folder, $prefix)
@@ -122,6 +122,7 @@ public function synchronize($params = array())
             foreach ($added as $bid => $object) {
                 $this->_updateLog($prefix.$object['uid'], $bid);
             }
+
             foreach ($deleted as $bid => $object_uid) {
                 // Check if the object is really gone from the folder.
                 // Otherwise we just deleted a duplicated object or updated the original one.
@@ -138,45 +139,41 @@ public function synchronize($params = array())
                     $bid, $object_uid)
                 );
                 $this->_history->log(
-                    $prefix.$object_uid, array('action' => 'delete', 'bid' => $bid), true
+                    $prefix . $object_uid, array('action' => 'delete', 'bid' => $bid), true
                 );
             }
         } else {
+            // Full sync. Either our timestamp is too old or the IMAP
+            // uidvalidity changed.
             $prefix = $this->_constructHistoryPrefix();
             if (empty($prefix)) {
                 return;
             }
-
             $this->_logger->debug(sprintf(
                 'History: Full history sync for user: %s, folder: %s, is_reset: %d, prefix: %s',
                 $user, $folder, $is_reset, $prefix)
             );
-
-            // Full sync. Either our timestamp is too old
-            // or the IMAP uidvalidity changed
             $this->_completeSynchronization($prefix, $is_reset);
         }
     }
 
     /**
      * Perform a complete synchronization.
-     * Also markes stale history entries as 'deleted'.
+     * Also marks stale history entries as 'deleted'.
      *
-     * @param string $prefix Horde_History prefix
-     * @param boolean $is_reset Flag to indicate if the UIDVALIDITY changed
-     *
-     * @return NULL
+     * @param string $prefix     Horde_History prefix
+     * @param boolean $is_reset  Flag to indicate if the UIDVALIDITY changed
      */
-    private function _completeSynchronization($prefix, $is_reset)
+    protected function _completeSynchronization($prefix, $is_reset)
     {
         $seen_objects = array();
         foreach ($this->_data->getObjectToBackend() as $object => $bid) {
-            $full_id = $prefix.$object;
+            $full_id = $prefix . $object;
             $this->_updateLog($full_id, $bid, $is_reset);
             $seen_objects[$full_id] = true;
         }
 
-        // cut of last ':'
+        // cut off last ':'
         $search_prefix = substr($prefix, 0, -1);
 
         // clean up history database: Mark stale entries as deleted
@@ -247,7 +244,7 @@ private function _constructHistoryPrefix()
             return '';
         }
 
-        $this->_prefix = $app.':'.$share_id.':';
+        $this->_prefix = $app . ':' . $share_id . ':';
 
         return $this->_prefix;
     }
@@ -255,7 +252,7 @@ private function _constructHistoryPrefix()
     /**
      * Map Kolab object type to horde application name.
      *
-     * @param string $type Kolab object type
+     * @param string $type  Kolab object type
      *
      * @return string The horde application name. Empty string if unknown
      */
@@ -277,14 +274,11 @@ private function _type2app($type)
     /**
      * Update the history log for an object.
      *
-     * @param string                           $object The object ID.
-     * @param string                           $bid    The backend ID of
-     *                                                 the object.
-     * @param bool                             $force  Force update
-     *
-     * @return NULL
+     * @param string $object  The object ID.
+     * @param string $bid     The backend ID of the object.
+     * @param boolean $force  Force update
      */
-    private function _updateLog($object, $bid, $force=false)
+    protected function _updateLog($object, $bid, $force = false)
     {
         $last = $this->_history->getLatestEntry($object);
         if ($last === false) {
@@ -321,4 +315,5 @@ private function _updateLog($object, $bid, $force=false)
             }
         }
     }
+
 }
diff --git a/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Cache.php b/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Cache.php
index 0df8342db9e..cae2ceab625 100644
--- a/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Cache.php
+++ b/framework/Kolab_Storage/lib/Horde/Kolab/Storage/Data/Query/History/Cache.php
@@ -39,8 +39,6 @@ class Horde_Kolab_Storage_Data_Query_History_Cache
      *   - last_sync:    (integer) Timestamp containing the time of last sync.
      *   - changes:      (array)   An array of arrays keyed by backend id
      *                             containing information about each change.
-     *
-     * @return NULL
      */
     public function synchronize($params = array())
     {
@@ -80,4 +78,5 @@ public function synchronize($params = array())
             );
         }
     }
+
 }
diff --git a/framework/Kolab_Storage/test/Horde/Kolab/Storage/Unit/Data/BaseTest.php b/framework/Kolab_Storage/test/Horde/Kolab/Storage/Unit/Data/BaseTest.php
index 3c1d79a4c5f..2310fcfa11c 100644
--- a/framework/Kolab_Storage/test/Horde/Kolab/Storage/Unit/Data/BaseTest.php
+++ b/framework/Kolab_Storage/test/Horde/Kolab/Storage/Unit/Data/BaseTest.php
@@ -384,7 +384,7 @@ public function testModify()
         $object = $data->getObject('UID');
         $this->assertEquals('modified', $object['summary']);
     }
-     
+
     public function testDuplicatesAddedObjects()
     {
         $data = $this->getMessageStorage()->getData('INBOX/Notes');