diff --git a/onyx/include/admin/exercice.php b/onyx/include/admin/exercice.php
index fa6858cd..415e1901 100644
--- a/onyx/include/admin/exercice.php
+++ b/onyx/include/admin/exercice.php
@@ -4,17 +4,33 @@ if(!defined('ONYX')) exit;
 
 $p = $out[0];
 
-if (isset($p[2]))
+//TODO maybe move the try catch to index.html ?
+try
 {
+  if (isset($p[2]))
+  {
     $tmp = explode("-", $p[2]);
     $id = intval($tmp[0]);
     if ($id == 0)
       return "404";
     $theme = new Theme($id);
     $template->assign("theme", $theme);
+  }
+
+  if (isset($p[3]))
+    $template->assign("ex", new Exercice($p[3], $theme));
+}
+catch (ThemeNotFoundException $e)
+{
+  return "404";
+}
+catch(ExerciceNotFoundException $e)
+{
+  return "404";
+}
+catch(ExerciceNotFoundException $e)
+{
+  return "404";
 }
 
-if (isset($p[3]))
-  $template->assign("ex", new Exercice($p[3], $theme));
-
 return SALT_ADMIN."/exercice";