diff --git a/src/de/steamwar/bungeecore/SubserverSystem.java b/src/de/steamwar/bungeecore/SubserverSystem.java
index b4ffbc4a..d5e85b03 100644
--- a/src/de/steamwar/bungeecore/SubserverSystem.java
+++ b/src/de/steamwar/bungeecore/SubserverSystem.java
@@ -89,7 +89,7 @@ public class SubserverSystem {
      * @return
      * The new started subserver.
      */
-    public static Subserver startArena(ArenaMode modus, String map, int eventFightID, int checkSchemID, int prepareSchemID, String serverName, String mapName, UUID player1, UUID player2, boolean ranked){
+    public static synchronized Subserver startArena(ArenaMode modus, String map, int eventFightID, int checkSchemID, int prepareSchemID, String serverName, String mapName, UUID player1, UUID player2, boolean ranked){
         //Generate missing parameters
         int port = freePort(FIRST_ARENA_PORT);
 
@@ -179,7 +179,7 @@ public class SubserverSystem {
         startArena(m, map, -1, checkSchemId, prepareSchemId, p.getName() + "s Bau", p.getName(), p.getUniqueId(), null, false).sendPlayer(p);
     }
 
-    private static void sendToBau(ProxiedPlayer p, UUID owner, String prototype, String worldFolder, String serverJar, String worldDir, String worldName, String xmx, String serverName){
+    private static synchronized void sendToBau(ProxiedPlayer p, UUID owner, String prototype, String worldFolder, String serverJar, String worldDir, String worldName, String xmx, String serverName){
         if(bauRunning(p, owner))
             return;