diff --git a/renderer.php b/renderer.php
index 698b87f..5cf6caa 100644
--- a/renderer.php
+++ b/renderer.php
@@ -477,7 +477,7 @@ function _highlight($type, $text, $language = null, $filename = null, $options =
             $this->doc .= '</a></dt>'.DOKU_LF.'<dd>';
         }
 
-        if($text{0} == "\n") {
+        if($text[0] == "\n") {
             $text = substr($text, 1);
         }
         if(substr($text, -1) == "\n") {
diff --git a/syntax/header.php b/syntax/header.php
index fb30608..193ef11 100755
--- a/syntax/header.php
+++ b/syntax/header.php
@@ -53,7 +53,7 @@ public function handle($match, $state, $pos, Doku_Handler $handler) {
         $level = 7 - strspn($title,'=');
         if($level < 1) $level = 1;
         $title = trim($title,'= ');
-        if ($this->getConf('revealjs_active') || $_GET['do']=='export_revealjs') {
+        if ($this->getConf('revealjs_active') || (isset($_GET['do']) && $_GET['do']=='export_revealjs')) {
             /* We are now on a reveal.js activated page and we want to do our
             own section handling to be able to get all relevant content from
             one slide into one edit section. Since sections are header driven,