diff --git a/core/tests/Drupal/KernelTests/AssertContentTrait.php b/core/tests/Drupal/KernelTests/AssertContentTrait.php
index b6f361c6f5949c109410febbb6568e76eb9d3b2f..66fb70a182586db5430aa5fe8d7e1d38c3ec2b40 100644
--- a/core/tests/Drupal/KernelTests/AssertContentTrait.php
+++ b/core/tests/Drupal/KernelTests/AssertContentTrait.php
@@ -56,7 +56,7 @@ protected function getRawContent() {
   /**
    * Sets the raw content (e.g. HTML).
    *
-   * @param string $content
+   * @param string|\Stringable $content
    *   The raw content to set.
    */
   protected function setRawContent($content) {