diff --git a/core/modules/field/lib/Drupal/field/FieldInfo.php b/core/modules/field/lib/Drupal/field/FieldInfo.php
index f791af8..23ad2c4 100644
--- a/core/modules/field/lib/Drupal/field/FieldInfo.php
+++ b/core/modules/field/lib/Drupal/field/FieldInfo.php
@@ -543,7 +543,7 @@ public function getBundleExtraFields($entity_type, $bundle) {
     drupal_alter('field_extra_fields', $extra);
 
     if (isset($extra[$entity_type][$bundle])) {
-      $info += $extra[$entity_type][$bundle];
+      $info = $extra[$entity_type][$bundle] + $info;
     }
 
     // Store in the 'static' and persistent caches.