diff --git a/helper.php b/helper.php
index 721422e..01147b7 100644
--- a/helper.php
+++ b/helper.php
@@ -131,7 +131,8 @@ class helper_plugin_semantic extends DokuWiki_Plugin
      */
     public function getAuthor()
     {
-        return ($this->meta['creator'] ? $this->meta['creator'] : null);
+        return ( array_key_exists('creator', $this->meta) ) ?
+            $this->meta['creator'] : null;
     }
 
     /**
@@ -141,7 +142,8 @@ class helper_plugin_semantic extends DokuWiki_Plugin
      */
     public function getAuthorID()
     {
-        return ($this->meta['user'] ? $this->meta['user'] : null);
+        return ( array_key_exists('user', $this->meta) ) ?
+            $this->meta['user'] : null;
     }
 
     /**