diff --git a/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java b/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java
index 1a4d1a1..69fde6a 100644
--- a/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java
+++ b/hsarback/src/de/hsadmin/autoconfig/AutoconfigAutodiscoverServlet.java
@@ -157,7 +157,7 @@ public class AutoconfigAutodiscoverServlet extends HttpServlet {
 		final Query mboxQuery = em.createQuery("SELECT mbox FROM UnixUsers mbox WHERE mbox.name = :target");
 		mboxQuery.setParameter("target", target);
 		final Object mboxResult = mboxQuery.getSingleResult();
-		if (mboxResult == null || !(mboxQuery instanceof UnixUser)) {
+		if (mboxResult == null || !(mboxResult instanceof UnixUser)) {
 			transaction.close();
 			throw new HSAdminException("no unique mailbox found");
 		}