diff --git a/core/tests/Drupal/Tests/BrowserTestBase.php b/core/tests/Drupal/Tests/BrowserTestBase.php
index ba08cd5..0689bad 100644
--- a/core/tests/Drupal/Tests/BrowserTestBase.php
+++ b/core/tests/Drupal/Tests/BrowserTestBase.php
@@ -1847,7 +1847,7 @@ protected function getTestMethodCaller() {
     $backtrace = debug_backtrace();
 
     // Remove all calls until we reach the current test class.
-    while (($caller = $backtrace[1]) &&
+    while (isset($backtrace[1]) && ($caller = $backtrace[1]) &&
       (!isset($caller['class']) || $caller['class'] !== get_class($this))
     ) {
       // We remove that call.