diff --git a/src/SM/StateMachine/StateMachine.php b/src/SM/StateMachine/StateMachine.php
index f06e4a7..1112f23 100644
--- a/src/SM/StateMachine/StateMachine.php
+++ b/src/SM/StateMachine/StateMachine.php
@@ -221,7 +221,7 @@ protected function callCallbacks(TransitionEvent $event, $position)
                 $callback = $this->callbackFactory->get($callback);
             }
 
-            $callback($event);
+            call_user_func($callback, $event);
         }
     }
 }