diff --git a/core/modules/views/src/Plugin/views/filter/InOperator.php b/core/modules/views/src/Plugin/views/filter/InOperator.php
index cff42b9627..1d1fe26db4 100644
--- a/core/modules/views/src/Plugin/views/filter/InOperator.php
+++ b/core/modules/views/src/Plugin/views/filter/InOperator.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\views\Plugin\views\filter;
 
+use Drupal\Component\Render\MarkupInterface;
 use Drupal\Component\Utility\Unicode;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\views\Plugin\views\display\DisplayPluginBase;
@@ -269,7 +270,7 @@ public function reduceValueOptions($input = NULL) {
         $options[$id] = $this->reduceValueOptions($option);
         continue;
       }
-      elseif (is_object($option)) {
+      elseif (is_object($option) && !($option instanceof MarkupInterface)) {
         $keys = array_keys($option->option);
         $key = array_shift($keys);
         if (isset($this->options['value'][$key])) {
diff --git a/core/modules/views/src/Plugin/views/filter/LanguageFilter.php b/core/modules/views/src/Plugin/views/filter/LanguageFilter.php
index 69fdc81a1f..f8536149b9 100644
--- a/core/modules/views/src/Plugin/views/filter/LanguageFilter.php
+++ b/core/modules/views/src/Plugin/views/filter/LanguageFilter.php
@@ -36,7 +36,7 @@ class LanguageFilter extends InOperator implements ContainerFactoryPluginInterfa
    * @param \Drupal\Core\Language\LanguageManagerInterface $language_manager
    *   The language manager.
    */
-  public function __construct($configuration, $plugin_id, $plugin_definition, LanguageManagerInterface $language_manager) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, LanguageManagerInterface $language_manager) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
 
     $this->languageManager = $language_manager;
@@ -62,7 +62,18 @@ public function getValueOptions() {
       $this->valueTitle = $this->t('Language');
       // Pass the current values so options that are already selected do not get
       // lost when there are changes in the language configuration.
-      $this->valueOptions = $this->listLanguages(LanguageInterface::STATE_ALL | LanguageInterface::STATE_SITE_DEFAULT | PluginBase::INCLUDE_NEGOTIATED, array_keys($this->value));
+      // Some languages are returned as TranslatableMarkup objects. Those will
+      // be cast to string to stay consistent with what other plugins expect,
+      // e.g. the "in_operator" plugin.
+      $this->valueOptions = array_map(
+        function ($value) {
+          return (string) $value;
+        },
+        $this->listLanguages(
+          LanguageInterface::STATE_ALL | LanguageInterface::STATE_SITE_DEFAULT | PluginBase::INCLUDE_NEGOTIATED,
+          array_keys($this->value)
+        )
+      );
     }
     return $this->valueOptions;
   }