diff --git a/tests/helper_test.php b/tests/helper_test.php
index a8dbc20..a1637bd 100644
--- a/tests/helper_test.php
+++ b/tests/helper_test.php
@@ -325,7 +325,7 @@ public function test_plain_text_search(): void {
     public function test_regex_search(): void {
         $this->resetAfterTest();
 
-        $searchstring = "https://example.com.au/\d+";
+        $searchstring = "https://example.com.au/[0-9]+";
 
         // Create a course.
         $course = $this->getDataGenerator()->create_course();