diff --git a/core/modules/ckeditor5/src/Plugin/Validation/Constraint/EnabledConfigurablePluginsConstraintValidator.php b/core/modules/ckeditor5/src/Plugin/Validation/Constraint/EnabledConfigurablePluginsConstraintValidator.php
index 9d610b9fc1f8848a54f84793a42f42aebd971d46..d4d350c27d635aea5c9c4324692163b18d79f5b3 100644
--- a/core/modules/ckeditor5/src/Plugin/Validation/Constraint/EnabledConfigurablePluginsConstraintValidator.php
+++ b/core/modules/ckeditor5/src/Plugin/Validation/Constraint/EnabledConfigurablePluginsConstraintValidator.php
@@ -51,7 +51,7 @@ public function validate($settings, Constraint $constraint) {
 
       if (!isset($plugin_settings[$id]) || empty($plugin_settings[$id])) {
         $this->context->buildViolation($constraint->message)
-          ->setParameter('%plugin_label', $definition->label())
+          ->setParameter('%plugin_label', (string) $definition->label())
           ->setParameter('%plugin_id', $id)
           ->atPath("plugins.$id")
           ->addViolation();
diff --git a/core/modules/ckeditor5/src/Plugin/Validation/Constraint/FundamentalCompatibilityConstraintValidator.php b/core/modules/ckeditor5/src/Plugin/Validation/Constraint/FundamentalCompatibilityConstraintValidator.php
index 0913e8cccd2184818ec7f55b8f3f577d70a3a255..0c35b73879d69c1b0208cca437b5506511260838 100644
--- a/core/modules/ckeditor5/src/Plugin/Validation/Constraint/FundamentalCompatibilityConstraintValidator.php
+++ b/core/modules/ckeditor5/src/Plugin/Validation/Constraint/FundamentalCompatibilityConstraintValidator.php
@@ -86,7 +86,7 @@ private function checkNoMarkupFilters(FilterFormatInterface $text_format, Fundam
     );
     foreach ($markup_filters as $markup_filter) {
       $this->context->buildViolation($constraint->noMarkupFiltersMessage)
-        ->setParameter('%filter_label', $markup_filter->getLabel())
+        ->setParameter('%filter_label', (string) $markup_filter->getLabel())
         ->setParameter('%filter_plugin_id', $markup_filter->getPluginId())
         ->addViolation();
     }
@@ -111,7 +111,7 @@ private function checkHtmlRestrictionsAreCompatible(FilterFormatInterface $text_
     if (!empty($forbidden_minimum_tags)) {
       $offending_filter = static::findHtmlRestrictorFilterForbiddingTags($text_format, $minimum_tags);
       $this->context->buildViolation($constraint->forbiddenElementsMessage)
-        ->setParameter('%filter_label', $offending_filter->getLabel())
+        ->setParameter('%filter_label', (string) $offending_filter->getLabel())
         ->setParameter('%filter_plugin_id', $offending_filter->getPluginId())
         ->addViolation();
     }
@@ -122,7 +122,7 @@ private function checkHtmlRestrictionsAreCompatible(FilterFormatInterface $text_
     if (!empty($not_allowed_minimum_tags)) {
       $offending_filter = static::findHtmlRestrictorFilterNotAllowingTags($text_format, $minimum_tags);
       $this->context->buildViolation($constraint->nonAllowedElementsMessage)
-        ->setParameter('%filter_label', $offending_filter->getLabel())
+        ->setParameter('%filter_label', (string) $offending_filter->getLabel())
         ->setParameter('%filter_plugin_id', $offending_filter->getPluginId())
         ->addViolation();
     }
diff --git a/core/modules/ckeditor5/src/Plugin/Validation/Constraint/ToolbarItemConditionsMetConstraintValidator.php b/core/modules/ckeditor5/src/Plugin/Validation/Constraint/ToolbarItemConditionsMetConstraintValidator.php
index 1987c862b4f6aba91485ed644848f184c4eef1f1..a45c427235a199f7a2a64ee5b0bc13ae9a93c2e8 100644
--- a/core/modules/ckeditor5/src/Plugin/Validation/Constraint/ToolbarItemConditionsMetConstraintValidator.php
+++ b/core/modules/ckeditor5/src/Plugin/Validation/Constraint/ToolbarItemConditionsMetConstraintValidator.php
@@ -61,7 +61,7 @@ public function validate($toolbar_item, Constraint $constraint) {
           $image_upload_settings = $text_editor->getImageUploadSettings();
           if (!isset($image_upload_settings['status']) || (bool) $image_upload_settings['status'] !== TRUE) {
             $this->context->buildViolation($constraint->imageUploadStatusRequiredMessage)
-              ->setParameter('%toolbar_item', $toolbar_item_label)
+              ->setParameter('%toolbar_item', (string) $toolbar_item_label)
               ->setInvalidValue($toolbar_item)
               ->addViolation();
           }
@@ -74,8 +74,8 @@ public function validate($toolbar_item, Constraint $constraint) {
               ? $filters->get($required_value)->getLabel()
               : $required_value;
             $this->context->buildViolation($constraint->filterRequiredMessage)
-              ->setParameter('%toolbar_item', $toolbar_item_label)
-              ->setParameter('%filter', $filter_label)
+              ->setParameter('%toolbar_item', (string) $toolbar_item_label)
+              ->setParameter('%filter', (string) $filter_label)
               ->setInvalidValue($toolbar_item)
               ->addViolation();
           }
@@ -101,7 +101,7 @@ public function validate($toolbar_item, Constraint $constraint) {
               $parameter = '%plugins';
             }
             $this->context->buildViolation($message)
-              ->setParameter('%toolbar_item', $toolbar_item_label)
+              ->setParameter('%toolbar_item', (string) $toolbar_item_label)
               ->setParameter($parameter, implode(', ', $missing_plugin_labels))
               ->setInvalidValue($toolbar_item)
               ->addViolation();