diff --git a/src/Services/ServiceListParameters/ServiceListParameter.php b/src/Services/ServiceListParameters/ServiceListParameter.php
index 6aa54635..1a1785f9 100644
--- a/src/Services/ServiceListParameters/ServiceListParameter.php
+++ b/src/Services/ServiceListParameters/ServiceListParameter.php
@@ -65,7 +65,7 @@ protected function appendParameter(?int $groupKey, ?string $groupType, string $n
     {
         if (! is_null($value))
         {
-            if (is_callable($value))
+            if (method_exists($this, $value))
             {
                 $this->serviceList->appendParameter($value($groupKey, $groupType));