diff --git a/src/main/java/io/akarin/server/misc/CopyOnWriteHashMap.java b/src/main/java/io/akarin/server/misc/CopyOnWriteHashMap.java
new file mode 100644
index 000000000..ca9c60ea7
--- /dev/null
+++ b/src/main/java/io/akarin/server/misc/CopyOnWriteHashMap.java
@@ -0,0 +1,184 @@
+package io.akarin.server.misc;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * A thread-safe version of {@link Map} in which all operations that change the
+ * Map are implemented by making a new copy of the underlying Map.
+ * <p/>
+ * While the creation of a new Map can be expensive, this class is designed for
+ * cases in which the primary function is to read data from the Map, not to
+ * modify the Map.  Therefore the operations that do not cause a change to this
+ * class happen quickly and concurrently.
+ *
+ * @author <a href="mailto:Kuzma.Deretuke@gmail.com">Kuzma Deretuke</a>
+ */
+public class CopyOnWriteHashMap<K, V> implements Map<K, V>, Serializable, Cloneable {
+    private static final long serialVersionUID = 5481095911554321115L;
+    private AtomicReference<Map<K, V>> internalMap = new AtomicReference<Map<K, V>>();
+
+    /**
+     * Creates a new instance of CopyOnWriteHashMap.
+     */
+    public CopyOnWriteHashMap() {
+        internalMap.set(new HashMap<K, V>());
+    }
+
+    /**
+     * Creates a new instance of CopyOnWriteHashMap with the specified initial size.
+     *
+     * @param initialCapacity The initial size of the Map.
+     */
+    public CopyOnWriteHashMap(int initialCapacity) {
+        internalMap.set(new HashMap<K, V>(initialCapacity));
+    }
+
+    /**
+     * Creates a new instance of CopyOnWriteHashMap in which the initial data,
+     * being held by this map, is contained in the supplied map.
+     *
+     * @param data A Map containing the initial contents to be placed into this class.
+     */
+    public CopyOnWriteHashMap(Map<K, V> data) {
+        internalMap.set(new HashMap<K, V>(data));
+    }
+
+    @Override
+    public V put(K key, V value) {
+        Map<K, V> oldMap;
+        Map<K, V> newMap;
+        V val;
+        do {
+            oldMap = internalMap.get();
+            newMap = new HashMap<K, V>(oldMap);
+            val = newMap.put(key, value);
+        }
+        while (!internalMap.compareAndSet(oldMap, newMap));
+        return val;
+    }
+
+    @Override
+    public V remove(Object key) {
+        Map<K, V> oldMap;
+        Map<K, V> newMap;
+        V val;
+        do {
+            oldMap = internalMap.get();
+            newMap = new HashMap<K, V>(oldMap);
+            val = newMap.remove(key);
+        }
+        while (!internalMap.compareAndSet(oldMap, newMap));
+        return val;
+    }
+
+    @Override
+    public void putAll(Map<? extends K, ? extends V> newData) {
+        Map<K, V> oldMap;
+        Map<K, V> newMap;
+        do {
+            oldMap = internalMap.get();
+            newMap = new HashMap<K, V>(oldMap);
+            newMap.putAll(newData);
+        }
+        while (!internalMap.compareAndSet(oldMap, newMap));
+    }
+
+    @Override
+    public void clear() {
+        internalMap.set(new HashMap<K, V>());
+    }
+
+    //
+    //  Below are methods that do not modify the internal map
+    //          
+
+    @Override
+    public int size() {
+        return internalMap.get().size();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return internalMap.get().isEmpty();
+    }
+
+    @Override
+    public boolean containsKey(Object key) {
+        return internalMap.get().containsKey(key);
+    }
+
+    @Override
+    public boolean containsValue(Object value) {
+        return internalMap.get().containsValue(value);
+    }
+
+    @Override
+    public V get(Object key) {
+        return internalMap.get().get(key);
+    }
+
+    @Override
+    public Set<K> keySet() {
+        return internalMap.get().keySet();
+    }
+
+    @Override
+    public Collection<V> values() {
+        return internalMap.get().values();
+    }
+
+    @Override
+    public Set<Entry<K, V>> entrySet() {
+        return internalMap.get().entrySet();
+    }
+
+    @Override
+    public int hashCode() {
+        return internalMap.get().hashCode();
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        return internalMap.get().equals(o);
+    }
+
+    @Override
+    public String toString() {
+        Map<K, V> map = internalMap.get();
+        Iterator<Entry<K, V>> i = map.entrySet().iterator();
+        if (!i.hasNext())
+            return "{}";
+
+        StringBuilder sb = new StringBuilder();
+        sb.append('{');
+        for (; ; ) {
+            Entry<K, V> e = i.next();
+            K key = e.getKey();
+            V value = e.getValue();
+            sb.append(key == this ? "(this Map)" : (key == map ? "(internal Map)" : key));
+            sb.append('=');
+            sb.append(value == this ? "(this Map)" : (value == map ? "(internal Map)" : value));
+            if (!i.hasNext())
+                return sb.append('}').toString();
+            sb.append(',').append(' ');
+        }
+    }
+
+    @Override
+    public Object clone() {
+        try {
+            CopyOnWriteHashMap<K, V> clone = (CopyOnWriteHashMap<K, V>) super.clone();
+            clone.internalMap = new AtomicReference<Map<K, V>>(new HashMap<K, V>(internalMap.get()));
+            return clone;
+        }
+        catch (CloneNotSupportedException e) {
+            throw new InternalError();
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/net/minecraft/server/JsonList.java b/src/main/java/net/minecraft/server/JsonList.java
index 2c69fffd9..5fc59cb41 100644
--- a/src/main/java/net/minecraft/server/JsonList.java
+++ b/src/main/java/net/minecraft/server/JsonList.java
@@ -14,6 +14,8 @@ import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
 import com.mojang.authlib.GameProfile;
 
+import io.akarin.server.misc.CopyOnWriteHashMap;
+
 import java.io.BufferedReader;
 import java.io.BufferedWriter;
 import java.io.File;
@@ -28,6 +30,8 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.concurrent.CopyOnWriteArrayList;
+
 import javax.annotation.Nullable;
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.builder.ToStringBuilder;
@@ -41,7 +45,7 @@ public class JsonList<K, V extends JsonListEntry<K>> {
     protected final Gson b;
     private final File c;
     // Paper - replace HashMap is ConcurrentHashMap
-    protected final Map<String, V> d = Maps.newConcurrentMap(); private final Map<String, V> getBackingMap() { return this.d; } // Paper - OBFHELPER
+    protected final Map<String, V> d = new CopyOnWriteHashMap<String, V>(); private final Map<String, V> getBackingMap() { return this.d; } // Paper - OBFHELPER // Akarin
     private boolean e = true;
     private static final ParameterizedType f = new ParameterizedType() {
         public Type[] getActualTypeArguments() {
diff --git a/work/Paper b/work/Paper
index 0181fb14b..ab8bbdfd8 160000
--- a/work/Paper
+++ b/work/Paper
@@ -1 +1 @@
-Subproject commit 0181fb14b6b52052194e2ee30dea5744f14ffc73
+Subproject commit ab8bbdfd8008deb0241d6ed1c62345c24ed34bd8