--- a/core/modules/field/field.module
+++ b/core/modules/field/field.module
@@ -503,14 +503,14 @@ function field_associate_fields($module) {
  *   The PluginManager object.
  */
 function field_get_plugin_manager($plugin_type) {
-  $plugin_types = drupal_static(__FUNCTION__, array());
+  $plugin_types = &drupal_static(__FUNCTION__, array());
 
   $classes = array(
     'widget' => 'Drupal\field\Plugin\Type\Widget\WidgetPluginManager',
   );
 
   if (isset($classes[$plugin_type])) {
-    if (empty($plugin_types[$plugin_type])) {
+    if (!isset($plugin_types[$plugin_type])) {
       $plugin_types[$plugin_type] = new $classes[$plugin_type]();
     }