diff -u b/core/lib/Drupal/Core/Render/Element/Details.php b/core/lib/Drupal/Core/Render/Element/Details.php --- b/core/lib/Drupal/Core/Render/Element/Details.php +++ b/core/lib/Drupal/Core/Render/Element/Details.php @@ -94,7 +94,7 @@ $element['#attributes']['class'][] = 'details--child-error'; $element['#title'] = \Drupal::translation()->formatPlural( count($element['#children_errors']), - '@title (contains an error)', + '@title (contains error)', '@title (contains @count errors)', [ '@title' => $element['#title'] diff -u b/core/tests/Drupal/FunctionalJavascriptTests/Core/Render/Element/VerticalTabsTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Core/Render/Element/VerticalTabsTest.php --- b/core/tests/Drupal/FunctionalJavascriptTests/Core/Render/Element/VerticalTabsTest.php +++ b/core/tests/Drupal/FunctionalJavascriptTests/Core/Render/Element/VerticalTabsTest.php @@ -26,7 +26,7 @@ $this->submitForm([], 'Submit'); - $web_assert->elementTextContains('css', '.vertical-tabs__menu-item-title .child-error-indicator', '(contains an error)'); + $web_assert->elementTextContains('css', '.vertical-tabs__menu-item-title .child-error-indicator', '(contains error)'); } }