diff --git a/plugins/calendar/drivers/kolab/kolab_driver.php b/plugins/calendar/drivers/kolab/kolab_driver.php
index cf6c2ff1..9b859bbd 100644
--- a/plugins/calendar/drivers/kolab/kolab_driver.php
+++ b/plugins/calendar/drivers/kolab/kolab_driver.php
@@ -2375,7 +2375,7 @@ class kolab_driver extends calendar_driver
     if (strlen($folder)) {
       $path_imap = explode($delim, $folder);
       array_pop($path_imap);  // pop off name part
-      $path_imap = implode($path_imap, $delim);
+      $path_imap = implode($delim, $path_imap);
 
       $options = $storage->folder_info($folder);
     }
diff --git a/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php b/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php
index 58e09731..710b5562 100644
--- a/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php
+++ b/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php
@@ -183,7 +183,7 @@ class kolab_addressbook_ui
         if ($action == 'edit') {
             $path_imap = explode($delim, $folder);
             $name      = rcube_charset::convert(array_pop($path_imap), 'UTF7-IMAP');
-            $path_imap = implode($path_imap, $delim);
+            $path_imap = implode($delim, $path_imap);
         }
         else { // create
             $path_imap = $folder;
diff --git a/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php b/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php
index cfc9e693..f6805eb0 100644
--- a/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php
+++ b/plugins/kolab_addressbook/lib/rcube_kolab_contacts.php
@@ -460,7 +460,7 @@ class rcube_kolab_contacts extends rcube_addressbook
 
         $scount = count($fields);
         // build key name regexp
-        $regexp = '/^(' . implode($fields, '|') . ')(?:.*)$/';
+        $regexp = '/^(' . implode('|', $fields) . ')(?:.*)$/';
 
         // pass query to storage if only indexed cols are involved
         // NOTE: this is only some rough pre-filtering but probably includes false positives
diff --git a/plugins/kolab_notes/kolab_notes_ui.php b/plugins/kolab_notes/kolab_notes_ui.php
index b39a57f4..dcbb35a6 100644
--- a/plugins/kolab_notes/kolab_notes_ui.php
+++ b/plugins/kolab_notes/kolab_notes_ui.php
@@ -306,7 +306,7 @@ class kolab_notes_ui
 
             $path_imap = explode($delim, $folder_name);
             array_pop($path_imap);  // pop off name part
-            $path_imap = implode($path_imap, $delim);
+            $path_imap = implode($delim, $path_imap);
         }
         else {
             $path_imap = '';
diff --git a/plugins/libkolab/lib/kolab_storage.php b/plugins/libkolab/lib/kolab_storage.php
index 192a510c..fa21692d 100644
--- a/plugins/libkolab/lib/kolab_storage.php
+++ b/plugins/libkolab/lib/kolab_storage.php
@@ -1371,8 +1371,8 @@ class kolab_storage
                 self::$subscriptions = self::$imap->list_folders_subscribed();
                 self::$with_tempsubs = true;
             }
-            self::$states = self::$subscriptions;
-            $folders = implode(self::$states, '**');
+            self::$states = (array) self::$subscriptions;
+            $folders = implode('**', self::$states);
             $rcube->user->save_prefs(array('kolab_active_folders' => $folders));
         }
 
@@ -1396,9 +1396,9 @@ class kolab_storage
         }
 
         // update user preferences
-        $folders = implode(self::$states, '**');
-        $rcube   = rcube::get_instance();
-        return $rcube->user->save_prefs(array('kolab_active_folders' => $folders));
+        $folders = implode('**', self::$states);
+
+        return rcube::get_instance()->user->save_prefs(array('kolab_active_folders' => $folders));
     }
 
     /**