diff --git a/Classes/Service/DefaultFieldResolver.php b/Classes/Service/DefaultFieldResolver.php
index 7cff094..006dc12 100644
--- a/Classes/Service/DefaultFieldResolver.php
+++ b/Classes/Service/DefaultFieldResolver.php
@@ -29,7 +29,7 @@ public static function resolve($source, array $args, $context, ResolveInfo $info
             $resolvedProperty = ObjectAccess::getProperty($source, $fieldName);
         }
 
-        if (is_callable($resolvedProperty)) {
+        if ($resolvedProperty instanceof \Closure) {
             return $resolvedProperty($source, $args, $context, $info);
         }