diff -u b/core/lib/Drupal/Core/Config/Config.php b/core/lib/Drupal/Core/Config/Config.php
--- b/core/lib/Drupal/Core/Config/Config.php
+++ b/core/lib/Drupal/Core/Config/Config.php
@@ -230,23 +230,2 @@
   }
-
-  /**
-   * Helper callback for array_walk_recursive().
-   *
-   * @param mixed $value
-   *   The configuration data value to validate.
-   * @param string $key
-   *   The key of the value.
-   * @param string $name
-   *   The name of the configuration object.
-   *
-   * @throws StorageException
-   *
-   * @see DatabaseStorage::validateData()
-   * @see FileStorage::validateData()
-   */
-  public static function validateValue($value, $key, $name) {
-    if (!is_scalar($value)) {
-      throw new StorageException(sprintf('Unsupported non-scalar value of type %s in key %s in config object %s', gettype($value), $key, $name));
-    }
-  }
 }