diff --git modules/user/user.module modules/user/user.module
index 4a636da..1ae69de 100644
--- modules/user/user.module
+++ modules/user/user.module
@@ -182,9 +182,11 @@ function user_uri($user) {
 function user_field_info_alter(&$info) {
   // Add the 'user_register_form' instance setting to all field types.
   foreach ($info as $field_type => $field_type_info) {
-    $info[$field_type]['instance_settings'] += array(
-      'user_register_form' => FALSE,
-    );
+    if (isset($info[$field_type]['instance_settings'])) {
+      $info[$field_type]['instance_settings'] += array(
+        'user_register_form' => FALSE,
+      );
+    }
   }
 }