diff --git a/core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php b/core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php
index a5a0233..41a7925 100644
--- a/core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php
+++ b/core/modules/system/src/Tests/Common/NoJavaScriptAnonymousTest.php
@@ -58,7 +58,7 @@ protected function assertNoJavaScript() {
     $this->assertTrue(empty($settings), 'drupalSettings is not set.');
 
     // Ensure no JavaScript file exists on the page.
-    $this->assertNoPattern('\.js/', 'No JavaScript files exists.');
+    $this->assertNoPattern('#\.js#', 'No JavaScript files exists.');
   }
 
 }