diff -u b/core/modules/comment/comment.module b/core/modules/comment/comment.module
--- b/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -144,7 +144,7 @@
 function comment_entity_base_field_info_alter(&$fields, EntityTypeInterface $entity_type) {
   // Provide a better default value for the moderation state field if the
   // content moderation is enabled for comments.
-  if (\Drupal::moduleHandler()->moduleExists('content_moderation') && \Drupal::service('content_moderation.moderation_information')->canModerateEntitiesOfEntityType($entity_type)) {
+  if (\Drupal::moduleHandler()->moduleExists('content_moderation') && \Drupal::service('content_moderation.moderation_information')->canModerateEntitiesOfEntityType($entity_type) && isset($fields['moderation_state'])) {
     $fields['moderation_state']->setDefaultValueCallback('comment_get_default_moderation_state');
   }
 }