diff --git a/core/lib/Drupal/Core/Entity/EntityConstraintViolationList.php b/core/lib/Drupal/Core/Entity/EntityConstraintViolationList.php
index 6edd31c..8e44a30 100644
--- a/core/lib/Drupal/Core/Entity/EntityConstraintViolationList.php
+++ b/core/lib/Drupal/Core/Entity/EntityConstraintViolationList.php
@@ -56,6 +56,7 @@ protected function violationOffsetsByField() {
       $this->violationOffsetsByField = [];
       foreach ($this as $offset => $violation) {
         if ($path = $violation->getPropertyPath()) {
+          // An example of $path might be 'title.0.value'.
           list($field_name) = explode('.', $path, 2);
           if ($this->entity->hasField($field_name)) {
             $this->violationOffsetsByField[$field_name][$offset] = $offset;