diff --git a/persona.module b/persona.module
index a8281bc..90235cc 100644
--- a/persona.module
+++ b/persona.module
@@ -507,8 +507,8 @@ function persona_block_view($delta) {
 /**
  * Implements hook_block_view_alter().
  */
-function persona_block_view_alter(array &$data, $block) {
-  if (variable_get('persona_takeover') && $block->module == 'user' && $block->delta == 'login') {
+function persona_block_view_alter(&$data, $block) {
+  if (isset($data) && variable_get('persona_takeover') && $block->module == 'user' && $block->delta == 'login') {
     $data['content'] = array();
   }
 }