diff --git a/QuestionsFile.class.php b/QuestionsFile.class.php
index f4228f3..904dffc 100644
--- a/QuestionsFile.class.php
+++ b/QuestionsFile.class.php
@@ -52,7 +52,11 @@ class QuestionsFile
    */
   public function get_question($id)
   {
-    return new Question($this->treeXML->getElementById($id));
+    $q = $this->treeXML->getElementById($id);
+    if (isset($q))
+      return new Question($q);
+    else
+      return NULL;
   }
 
   /**