diff --git a/lib/microappplugin.php b/lib/microappplugin.php
index ab6d565157..0266f5184c 100644
--- a/lib/microappplugin.php
+++ b/lib/microappplugin.php
@@ -512,7 +512,7 @@ abstract class MicroAppPlugin extends Plugin
     function onEndActivityObjectOutputJson(ActivityObject $obj, array &$out)
     {
         if (in_array($obj->type, $this->types())) {
-            $this->activityObjectOutputJson($obj, &$out);
+            $this->activityObjectOutputJson($obj, $out);
         }
         return true;
     }