Fix reference to non-existing class rcube_output_html (#1488948)

1 files changed, 1 insertions, 1 deletions

diff --git a/plugins/newmail_notifier/newmail_notifier.php b/plugins/newmail_notifier/newmail_notifier.php
index 942421166..2c7ba949d 100644
--- a/plugins/newmail_notifier/newmail_notifier.php
+++ b/plugins/newmail_notifier/newmail_notifier.php
@@ -51,7 +51,7 @@ class newmail_notifier extends rcube_plugin
         else { // if ($this->rc->task == 'mail') {
             $this->add_hook('new_messages', array($this, 'notify'));
             // add script when not in ajax and not in frame
-            if (is_a($this->rc->output, 'rcube_output_html') && empty($_REQUEST['_framed'])) {
+            if ($this->rc->output->type == 'html' && empty($_REQUEST['_framed'])) {
                 $this->add_texts('localization/');
                 $this->rc->output->add_label('newmail_notifier.title', 'newmail_notifier.body');
                 $this->include_script('newmail_notifier.js');