diff --git a/40-PicoSearch.php b/40-PicoSearch.php
index 01a5354..be457a3 100644
--- a/40-PicoSearch.php
+++ b/40-PicoSearch.php
@@ -28,7 +28,7 @@ class PicoSearch extends AbstractPicoPlugin
     public function onRequestUrl(&$url)
     {
         // If form was submitted without being intercepted by JavaScript, redirect to the canonical search URL.
-        if (preg_match('~^(.+/)?search$~', $url) && $_GET['q']) {
+        if (preg_match('~^(.+/)?search$~', $url) && isset($_GET['q'])) {
             header('Location: ' . $this->getPico()->getBaseUrl() . $url . '/' . urlencode($_GET['q']));
             exit;
         }