--- a/question_types/quiz_question/quiz_question.module
+++ b/question_types/quiz_question/quiz_question.module
@@ -90,15 +90,15 @@ function quiz_question_node_access($node, $op, $account) {
          return NODE_ACCESS_DENY;
        }
     case 'create':
-      if (in_array($node, $question_types) && !user_access('create quiz', $account)) {
+      if (is_object($node) && in_array($node->type, $question_types) && !user_access('create quiz', $account)) {
         return NODE_ACCESS_DENY;
       }
     case 'update':
-      if (in_array($node, $question_types) && (user_access('edit any quiz', $account) || (user_access('edit own quiz', $account) && ($account->uid == $node->uid)))) {
+      if (is_object($node) && in_array($node->type, $question_types) && (user_access('edit any quiz', $account) || (user_access('edit own quiz', $account) && ($account->uid == $node->uid)))) {
         return NODE_ACCESS_ALLOW;
       }
     case 'delete':
-      if (in_array($node, $question_types) && (user_access('delete any quiz', $account) || (user_access('delete own quiz', $account) && ($account->uid == $node->uid)))) {
+      if (is_object($node) && in_array($node->type, $question_types) && (user_access('delete any quiz', $account) || (user_access('delete own quiz', $account) && ($account->uid == $node->uid)))) {
         return NODE_ACCESS_ALLOW;
       }
   }