diff --git a/core/lib/Drupal/Core/Database/StatementPrefetch.php b/core/lib/Drupal/Core/Database/StatementPrefetch.php
index ef1593c..f601f74 100644
--- a/core/lib/Drupal/Core/Database/StatementPrefetch.php
+++ b/core/lib/Drupal/Core/Database/StatementPrefetch.php
@@ -37,13 +37,20 @@ class StatementPrefetch implements Iterator, StatementInterface {
   /**
    * Reference to the database connection object for this statement.
    *
-   * The name $dbh is inherited from PDOStatement.
+   * This is part of the public interface of PDOStatement.
    *
-   * @var Drupal\Core\Database\Connection
+   * @var PDO
    */
   public $dbh;
 
   /**
+   * Reference to the Drupal database connection object for this statement.
+   *
+   * @var Drupal\Core\Database\Connection
+   */
+  protected $connection;
+
+  /**
    * Main data store.
    *
    * @var Array