diff --git a/framework/core/src/Extend/Conditional.php b/framework/core/src/Extend/Conditional.php
index f9098430a0..55584beebe 100644
--- a/framework/core/src/Extend/Conditional.php
+++ b/framework/core/src/Extend/Conditional.php
@@ -82,15 +82,12 @@ public function extend(Container $container, Extension $extension = null)
             if ($condition['condition']) {
                 $extenders = $condition['extenders'];
 
-                if (is_string($extenders) && class_exists($extenders) && method_exists($extenders, '__invoke')) {
-                    $result = $container->call($extenders);
-                    $extenders = is_array($result) ? $result : [$result];
+                if (is_string($extenders)) {
+                    $extenders = $container->call($extenders);
                 } elseif (is_callable($extenders)) {
                     $extenders = $container->call($extenders);
                 }
 
-                assert(is_array($extenders), 'Extenders should be an array after resolution.');
-
                 foreach ($extenders as $extender) {
                     $extender->extend($container, $extension);
                 }