diff --git a/core/components/ace/elements/plugins/ace.plugin.php b/core/components/ace/elements/plugins/ace.plugin.php
index 1acfabb..46d303e 100644
--- a/core/components/ace/elements/plugins/ace.plugin.php
+++ b/core/components/ace/elements/plugins/ace.plugin.php
@@ -103,7 +103,7 @@
         $modxTags = $extension == 'tpl';
         break;
     case 'OnDocFormPrerender':
-        if (!$modx->controller->resourceArray) {
+        if (!$modx->controller || !isset($modx->controller->resourceArray)) {
             return;
         }
         $field = 'ta';