diff --git a/core/modules/system/src/Tests/Routing/DestinationTest.php b/core/modules/system/src/Tests/Routing/DestinationTest.php
index a590d62..56a7edf 100644
--- a/core/modules/system/src/Tests/Routing/DestinationTest.php
+++ b/core/modules/system/src/Tests/Routing/DestinationTest.php
@@ -72,9 +72,9 @@ public function testDestination() {
       $this->assertIdentical($test_case['output'], $post_output, $test_case['message']);
     }
 
-    // Make sure that 404 pages do not populate $_GET['destination'] with
-    // external URLs.
-    \Drupal::configFactory()->getEditable('system.site')->set('page.404', 'system-test/get-destination')->save();
+    // Make sure that 404 pages do not populate $_GET['_exception_location']
+    // with external URLs.
+    \Drupal::configFactory()->getEditable('system.site')->set('page.404', 'system-test/get-exception-location')->save();
     $this->drupalGet('http://example.com', ['external' => FALSE]);
     $this->assertResponse(404);
     $this->assertIdentical(Url::fromRoute('<front>')->toString(), $this->getRawContent(), 'External URL is not allowed on 404 pages.');
diff --git a/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php b/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
index 5ac7ca0..0fab6aa 100644
--- a/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
+++ b/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
@@ -130,6 +130,20 @@ public function getDestination(Request $request) {
   }
 
   /**
+   * Controller to return $_GET['_exception_location'] for testing.
+   *
+   * @param \Symfony\Component\HttpFoundation\Request $request
+   *   The request.
+   *
+   * @return \Symfony\Component\HttpFoundation\Response
+   *   The response.
+   */
+  public function getExceptionLocation(Request $request) {
+    $response = new Response($request->query->get('_exception_location'));
+    return $response;
+  }
+
+  /**
    * Controller to return $_REQUEST['destination'] for testing.
    *
    * @param \Symfony\Component\HttpFoundation\Request $request
diff --git a/core/modules/system/tests/modules/system_test/system_test.routing.yml b/core/modules/system/tests/modules/system_test/system_test.routing.yml
index ecb9921..ba22633 100644
--- a/core/modules/system/tests/modules/system_test/system_test.routing.yml
+++ b/core/modules/system/tests/modules/system_test/system_test.routing.yml
@@ -116,6 +116,13 @@ system_test.get_destination:
   requirements:
     _access: 'TRUE'
 
+system_test.get_exception_location:
+  path: '/system-test/get-exception-location'
+  defaults:
+    _controller: '\Drupal\system_test\Controller\SystemTestController::getExceptionLocation'
+  requirements:
+    _access: 'TRUE'
+
 system_test.permission_dependent_content:
   path: '/system-test/permission-dependent-content'
   defaults: