diff --git a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
index 092d0cd..c615a21 100644
--- a/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/JavascriptTestBase.php
@@ -47,16 +47,18 @@ protected function initMink() {
    * {@inheritdoc}
    */
   protected function tearDown() {
-    // Wait for all requests to finish. It is possible that an AJAX request is
-    // still on-going.
-    $result = $this->getSession()->wait(5000, '(typeof(jQuery)=="undefined" || (0 === jQuery.active && 0 === jQuery(\':animated\').length))');
-    if (!$result) {
-      // If the wait is unsuccessful, there may still be an AJAX request in
-      // progress. If we tear down now, then this AJAX request may fail with
-      // missing database tables, because tear down will have removed them. Rather
-      // than allow it to fail, throw an explicit exception now explaining what
-      // the problem is.
-      throw new \RuntimeException('Unfinished AJAX requests whilst tearing down a test');
+    if ($this->mink) {
+      // Wait for all requests to finish. It is possible that an AJAX request is
+      // still on-going.
+      $result = $this->getSession()->wait(5000, '(typeof(jQuery)=="undefined" || (0 === jQuery.active && 0 === jQuery(\':animated\').length))');
+      if (!$result) {
+        // If the wait is unsuccessful, there may still be an AJAX request in
+        // progress. If we tear down now, then this AJAX request may fail with
+        // missing database tables, because tear down will have removed them. Rather
+        // than allow it to fail, throw an explicit exception now explaining what
+        // the problem is.
+        throw new \RuntimeException('Unfinished AJAX requests whilst tearing down a test');
+      }
     }
     parent::tearDown();
   }
diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index ba08cd5..64a2219 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -263,7 +263,9 @@
   /**
    * Mink session manager.
    *
-   * @var \Behat\Mink\Mink
+   * This will not be initialized if there was an error during the test setup.
+   *
+   * @var \Behat\Mink\Mink|null
    */
   protected $mink;