diff --git a/node_class.module b/node_class.module
index a809d35c6cc06200f0d9e5717d1e592ae072f875..a6dd2b32c60b6110e85d35d071bc60c219097e68 100644
--- a/node_class.module
+++ b/node_class.module
@@ -27,9 +27,11 @@ function node_class($node) {
  * Gets CSS class information for a given node.
  */
 function node_class_attributes($node) {
-  $ret = db_query('SELECT css_class FROM {node_class} WHERE nid = :nid',
-    array(':nid' => $node->nid))->fetchField();
-  return $ret ? $ret : '';
+  if (isset($node->nid)) {
+    $ret = db_query('SELECT css_class FROM {node_class} WHERE nid = :nid',
+      array(':nid' => $node->nid))->fetchField();
+  }
+  return !empty($ret) ? $ret : '';
 }

 /**