diff --git a/core/modules/comment/src/CommentFieldItemList.php b/core/modules/comment/src/CommentFieldItemList.php
index 5c0297b..cac425d 100644
--- a/core/modules/comment/src/CommentFieldItemList.php
+++ b/core/modules/comment/src/CommentFieldItemList.php
@@ -30,4 +30,16 @@ public function get($index) {
     return parent::get($index);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function offsetExists($offset) {
+    // For consistency with what happens in get(), we force offsetExists() to
+    // be TRUE for delta 0.
+    if ($offset === 0) {
+      return TRUE;
+    }
+    return parent::offsetExists($offset);
+  }
+
 }