diff --git a/index.php b/index.php
index 73d7901..36e4a3a 100644
--- a/index.php
+++ b/index.php
@@ -70,8 +70,10 @@ if (isset($_GET['f'])) {
   if ($_GET['f'] != '') {
     $tr = array('(' => '\(', ')' => '\)');
     $f = strtr($_GET['f'], $tr);
-    $files = array_values(preg_grep('/.*'.$f.'.*/i', $files));
-    $dirs = array_values(preg_grep('/.*'.$f.'.*/i', $dirs));
+    if (!empty($files))
+      $files = array_values(preg_grep('/.*'.$f.'.*/i', $files));
+    if (!empty($dirs))
+      $dirs = array_values(preg_grep('/.*'.$f.'.*/i', $dirs));
     $filter='&f='.$_GET['f'];
   }
 }