diff --git a/library/Businessprocess/BusinessProcess.php b/library/Businessprocess/BusinessProcess.php
index d321cb8..1961a4b 100644
--- a/library/Businessprocess/BusinessProcess.php
+++ b/library/Businessprocess/BusinessProcess.php
@@ -94,7 +94,7 @@ class BusinessProcess
         return $this;
     }
 
-    public function retrieveStatesFromBackend($backend)
+    public function retrieveStatesFromBackend(MonitoringBackend $backend)
     {
         $this->backend = $backend;
         // TODO: Split apart, create a dedicated function.