diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php
index b61b301..ddf0e91 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php
@@ -72,4 +72,14 @@ public function getConstraints() {
     return $constraints;
   }
 
+  /**
+   * Avoid to serialize the instance; unecessary and breaks in PHP 5.4.
+   */
+  public function __sleep() {
+    $vars = array_keys(get_class_vars(get_class($this)));
+    $this->instance = NULL;
+    unset($vars['instance']);
+    return $vars;
+  }
+
 }