diff --git a/httprl.module b/httprl.module
index b36bec6..115faa4 100644
--- a/httprl.module
+++ b/httprl.module
@@ -1188,7 +1188,9 @@ function httprl_run_callback(&$result) {
   ob_end_clean();
 
   // Add options back into the callback array.
-  array_unshift($result->options['callback'], $callback_options);
+  if (isset($result->options['callback'])) {
+    array_unshift($result->options['callback'], $callback_options);
+  }
 }
 
 /**