diff --git a/plugins/managesieve/managesieve.js b/plugins/managesieve/managesieve.js
index cd0d5f3ca..8340b179d 100644
--- a/plugins/managesieve/managesieve.js
+++ b/plugins/managesieve/managesieve.js
@@ -930,7 +930,7 @@ function sieve_form_init()
 
 rcube_webmail.prototype.managesieve_create = function(force)
 {
-  if (!force && this.env.action != 'show' && !$('#'+this.env.contentframe).is(':visible')) {
+  if (!force && this.env.action != 'show') {
     var uid = this.message_list.get_single_selection(),
       lock = this.set_busy(true, 'loading');
 
diff --git a/plugins/managesieve/managesieve.php b/plugins/managesieve/managesieve.php
index 478f26b00..7a307e1fe 100644
--- a/plugins/managesieve/managesieve.php
+++ b/plugins/managesieve/managesieve.php
@@ -51,7 +51,9 @@ class managesieve extends rcube_plugin
         }
         else if ($this->rc->task == 'mail') {
             // register message hook
-            $this->add_hook('message_headers_output', array($this, 'mail_headers'));
+            if ($this->rc->action == 'show') {
+                $this->add_hook('message_headers_output', array($this, 'mail_headers'));
+            }
 
             // inject Create Filter popup stuff
             if (empty($this->rc->action) || $this->rc->action == 'show'
@@ -192,9 +194,10 @@ class managesieve extends rcube_plugin
     function managesieve_actions()
     {
         // handle fetching email headers for the new filter form
-        if ($uid = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_GPC)) {
-            $mailbox = $this->rc->get_storage()->get_folder();
-            $message = new rcube_message($uid, $mailbox);
+        if ($uid = rcube_utils::get_input_value('_uid', rcube_utils::INPUT_POST)) {
+            $uids    = rcmail::get_uids();
+            $mailbox = key($uids);
+            $message = new rcube_message($uids[$mailbox][0], $mailbox);
             $headers = $this->parse_headers($message->headers);
 
             $this->rc->output->set_env('sieve_headers', $headers);