diff -u b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
--- b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityDatabaseStorage.php
@@ -121,10 +121,6 @@
    * {@inheritdoc}
    */
   protected function doLoadMultiple(array $ids = NULL) {
-    if ($ids !== NULL) {
-      $ids = $this->cleanIds($ids);
-    }
-
     // Build and execute the query.
     $records = $this
       ->buildQuery($ids)
@@ -135,30 +131,6 @@
   }
 
   /**
-   * Verifies that the specified entity IDs are of the correct data type for the
-   * entity type.
-   *
-   * @param array $ids
-   *   The entity IDs to verify.
-   * @return array
-   *   The sanitized list of entity IDs.
-   */
-  protected function cleanIds(array $ids) {
-    $keys = $this->entityType->getKeys();
-    $bundle = $keys['bundle'] ? $keys['bundle'] : $this->entityTypeId;
-
-    $definitions = $this->entityManager->getFieldDefinitions($this->entityTypeId, $bundle);
-    $info = $this->entityManager->getDefinition($this->entityTypeId);
-    $id_definition = $definitions[$info->getKey('id')];
-
-    if (!empty($ids) && $id_definition->getType() == 'integer') {
-      $ids = array_filter($ids, 'is_numeric');
-      $ids = array_map('intval', $ids);
-    }
-    return $ids;
-  }
-
-  /**
    * Maps from storage records to entity objects.
    *
    * This will attach fields, if the entity is fieldable. It calls
@@ -367,6 +339,10 @@
    * {@inheritdoc}
    */
   protected function doLoadMultiple(array $ids = NULL) {
+    if ($ids !== NULL) {
+      $ids = $this->cleanIds($ids);
+    }
+
     // Build and execute the query.
     $records = $this
       ->buildQuery($ids)
@@ -377,6 +353,43 @@
   }
 
   /**
+   * Verifies that the specified entity IDs are of the correct data type for the
+   * entity type.
+   *
+   * The identifier verification provided by this method has been introduced
+   * as Drupal core used to rely on the database to facilitate this, which worked
+   * correctly with MySQL but would lead to errors with other DBMS such as
+   * PostgeSQL.
+   *
+   * @param array $ids
+   *   The entity IDs to verify.
+   * @return array
+   *   The sanitized list of entity IDs.
+   */
+  protected function cleanIds(array $ids) {
+    $keys = $this->entityType->getKeys();
+    $bundle = $keys['bundle'] ? $keys['bundle'] : $this->entityTypeId;
+
+    $definitions = $this->entityManager->getFieldDefinitions($this->entityTypeId, $bundle);
+    $info = $this->entityManager->getDefinition($this->entityTypeId);
+    $id_definition = $definitions[$info->getKey('id')];
+
+    if (!empty($ids)) {
+      switch ($id_definition->getType()) {
+        case 'integer':
+          $ids = array_filter($ids, 'is_numeric');
+          $ids = array_map('intval', $ids);
+          break;
+        case 'string':
+          $ids = array_filter($ids, 'is_string');
+          $ids = array_map('strval', $ids);
+          break;
+      }
+    }
+    return $ids;
+  }
+
+  /**
    * Maps from storage records to entity objects.
    *
    * This will attach fields, if the entity is fieldable. It calls