diff --git a/plugins/kolab_2fa/kolab_2fa.php b/plugins/kolab_2fa/kolab_2fa.php
index f1794588..f3f85197 100644
--- a/plugins/kolab_2fa/kolab_2fa.php
+++ b/plugins/kolab_2fa/kolab_2fa.php
@@ -404,7 +404,7 @@ class kolab_2fa extends rcube_plugin
         $this->register_handler('plugin.highsecuritydialog', array($this, 'settings_highsecuritydialog'));
 
         $this->include_script('kolab2fa.js');
-        $this->include_stylesheet($this->local_skin_path() . '/kolab2fa.css', true);
+        $this->include_stylesheet($this->local_skin_path() . '/kolab2fa.css');
 
         if ($this->check_secure_mode()) {
             $this->api->output->set_env('session_secured', $_SESSION['kolab_2fa_secure_mode']);
diff --git a/plugins/kolab_activesync/kolab_activesync_ui.php b/plugins/kolab_activesync/kolab_activesync_ui.php
index 4959e4a9..636f97c6 100644
--- a/plugins/kolab_activesync/kolab_activesync_ui.php
+++ b/plugins/kolab_activesync/kolab_activesync_ui.php
@@ -39,7 +39,7 @@ class kolab_activesync_ui
         $skin_path       = $this->plugin->local_skin_path() . '/';
         $this->skin_path = 'plugins/kolab_activesync/' . $skin_path;
 
-        $this->plugin->include_stylesheet($skin_path . 'config.css', true);
+        $this->plugin->include_stylesheet($skin_path . 'config.css');
     }
 
     public function device_list($attrib = array())
diff --git a/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php b/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php
index 0454e8b0..726b66cf 100644
--- a/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php
+++ b/plugins/kolab_addressbook/lib/kolab_addressbook_ui.php
@@ -52,7 +52,7 @@ class kolab_addressbook_ui
 
         if (empty($this->rc->action)) {
             // Include stylesheet (for directorylist)
-            $this->plugin->include_stylesheet($this->plugin->local_skin_path().'/kolab_addressbook.css', true);
+            $this->plugin->include_stylesheet($this->plugin->local_skin_path().'/kolab_addressbook.css');
 
             // include kolab folderlist widget if available
             if (in_array('libkolab', $this->plugin->api->loaded_plugins())) {
diff --git a/plugins/kolab_delegation/kolab_delegation.php b/plugins/kolab_delegation/kolab_delegation.php
index 306564aa..0752d0cf 100644
--- a/plugins/kolab_delegation/kolab_delegation.php
+++ b/plugins/kolab_delegation/kolab_delegation.php
@@ -78,7 +78,7 @@ class kolab_delegation extends rcube_plugin
                 }
 
                 $this->skin_path = $this->local_skin_path();
-                $this->include_stylesheet($this->skin_path . '/style.css', true);
+                $this->include_stylesheet($this->skin_path . '/style.css');
             }
         }
         // Calendar/Tasklist plugin UI bindings
diff --git a/plugins/libkolab/libkolab.php b/plugins/libkolab/libkolab.php
index a3152915..cee2df9c 100644
--- a/plugins/libkolab/libkolab.php
+++ b/plugins/libkolab/libkolab.php
@@ -58,7 +58,7 @@ class libkolab extends rcube_plugin
         $this->add_texts('localization/', false);
 
         if ($rcmail->output->type == 'html') {
-            $this->include_stylesheet($this->local_skin_path() . '/libkolab.css', true);
+            $this->include_stylesheet($this->local_skin_path() . '/libkolab.css');
         }
 
         // embed scripts and templates for email message audit trail