diff --git a/htmlmail.module b/htmlmail.module
index e153172..56976eb 100644
--- a/htmlmail.module
+++ b/htmlmail.module
@@ -100,8 +100,10 @@ function htmlmail_theme() {
  * @see htmlmail.tpl.php
  */
 function template_preprocess_htmlmail(array &$variables) {
-  $message = $variables['message'];
-  $variables += $message;
+  if (isset($variables['message'])) {
+    $message = $variables['message'];
+    $variables += $message;
+  }
   $variables['debug'] = variable_get('htmlmail_debug', '0');
   $variables['theme'] = htmlmail_get_selected_theme($variables);
   $variables['module_path'] = drupal_get_path('module', 'htmlmail');