diff --git a/src/Runner/ErrorHandler.php b/src/Runner/ErrorHandler.php
index 2cf8d6fb1d0..7fa66d32f22 100644
--- a/src/Runner/ErrorHandler.php
+++ b/src/Runner/ErrorHandler.php
@@ -400,6 +400,13 @@ private function stackTrace(): string
         $excludeList = new ExcludeList(true);
 
         foreach ($this->errorStackTrace() as $frame) {
+            /**
+             * @see https://github.com/sebastianbergmann/phpunit/issues/6043
+             */
+            if (!isset($frame['file'])) {
+                continue;
+            }
+
             if ($excludeList->isExcluded($frame['file'])) {
                 continue;
             }