diff --git a/src/de/steamwar/bungeecore/listeners/mods/Fabric.java b/src/de/steamwar/bungeecore/listeners/mods/Fabric.java
index 7973fd1..e683040 100644
--- a/src/de/steamwar/bungeecore/listeners/mods/Fabric.java
+++ b/src/de/steamwar/bungeecore/listeners/mods/Fabric.java
@@ -48,8 +48,10 @@ public class Fabric extends BasicListener {
 
     private final Set<String> neededMods = new HashSet<>();
 
-    public static final Map<ProxiedPlayer, Integer> checkedPlayers = new HashMap<>();
-    public static final Map<ProxiedPlayer, Long> expectPluginMessage = new HashMap<>();
+    private static final Map<ProxiedPlayer, Integer> checkedPlayers = new HashMap<>();
+    private static final Map<ProxiedPlayer, Long> expectPluginMessage = new HashMap<>();
+
+    private static final Object OBJECT = new Object();
 
     {
         neededMods.add("java");
@@ -58,10 +60,12 @@ public class Fabric extends BasicListener {
         neededMods.add("steamwarmodsender");
 
         BungeeCord.getInstance().getScheduler().schedule(BungeeCore.get(), () -> {
-            for (Map.Entry<ProxiedPlayer, Long> entry : expectPluginMessage.entrySet()) {
-                if (System.currentTimeMillis() - entry.getValue() > TimeUnit.SECONDS.toMillis(20)) {
-                    banPlayer(SteamwarUser.get(entry.getKey()), entry.getKey());
-                    return;
+            synchronized (OBJECT) {
+                for (Map.Entry<ProxiedPlayer, Long> entry : expectPluginMessage.entrySet()) {
+                    if (System.currentTimeMillis() - entry.getValue() > TimeUnit.SECONDS.toMillis(20)) {
+                        banPlayer(SteamwarUser.get(entry.getKey()), entry.getKey());
+                        return;
+                    }
                 }
             }
         }, 0, 1, TimeUnit.SECONDS);
@@ -79,9 +83,13 @@ public class Fabric extends BasicListener {
         ProxiedPlayer player = (ProxiedPlayer) e.getSender();
         SteamwarUser user = SteamwarUser.get(player.getUniqueId());
 
-        if (expectPluginMessage.containsKey(player) && !checkedPlayers.containsKey(player)) {
-            banPlayer(user, player);
-            return;
+        if (!checkedPlayers.containsKey(player)) {
+            synchronized (OBJECT) {
+                if (expectPluginMessage.containsKey(player)) {
+                    banPlayer(user, player);
+                    return;
+                }
+            }
         }
 
         List<Mod> mods = new LinkedList<>();
@@ -148,7 +156,9 @@ public class Fabric extends BasicListener {
     @EventHandler
     public void onServerSwitchEvent(ServerSwitchEvent e) {
         if (e.getFrom() == null) return;
-        expectPluginMessage.put(e.getPlayer(), System.currentTimeMillis());
+        synchronized (OBJECT) {
+            expectPluginMessage.put(e.getPlayer(), System.currentTimeMillis());
+        }
     }
 
     private boolean isSortedAlphabetically(List<Mod> mods) {
@@ -177,4 +187,11 @@ public class Fabric extends BasicListener {
                 true);
         BungeeCore.log(Level.SEVERE,Message.parse("MODIFICATION_BAN_LOG", player, user.getUserName()));
     }
+
+    public static void remove(ProxiedPlayer player) {
+        synchronized (OBJECT) {
+            checkedPlayers.remove(player);
+            expectPluginMessage.remove(player);
+        }
+    }
 }
diff --git a/src/de/steamwar/bungeecore/listeners/mods/ModLoaderBlocker.java b/src/de/steamwar/bungeecore/listeners/mods/ModLoaderBlocker.java
index 00e076e..286ab01 100644
--- a/src/de/steamwar/bungeecore/listeners/mods/ModLoaderBlocker.java
+++ b/src/de/steamwar/bungeecore/listeners/mods/ModLoaderBlocker.java
@@ -28,7 +28,6 @@ import net.md_5.bungee.api.event.PluginMessageEvent;
 import net.md_5.bungee.api.event.ServerSwitchEvent;
 import net.md_5.bungee.event.EventHandler;
 
-import java.nio.charset.StandardCharsets;
 import java.util.HashSet;
 import java.util.Set;
 
@@ -58,8 +57,7 @@ public class ModLoaderBlocker extends BasicListener {
 
     @EventHandler
     public void onDisconnect(PlayerDisconnectEvent e){
-        Fabric.checkedPlayers.remove(e.getPlayer());
-        Fabric.expectPluginMessage.remove(e.getPlayer());
+        Fabric.remove(e.getPlayer());
         Storage.fabricPlayers.remove(e.getPlayer());
     }