diff --git a/src/main/java/carpet/script/CarpetScriptHost.java b/src/main/java/carpet/script/CarpetScriptHost.java
index fe54ef7a..fb307910 100644
--- a/src/main/java/carpet/script/CarpetScriptHost.java
+++ b/src/main/java/carpet/script/CarpetScriptHost.java
@@ -267,10 +267,6 @@ public class CarpetScriptHost extends ScriptHost
     @Override
     public void onClose()
     {
-        super.onClose();
-        if (this.saveTimeout > 0)
-            dumpState();
-
         FunctionValue closing = getFunction("__on_close");
         if (closing != null)
         {
@@ -307,7 +303,9 @@ public class CarpetScriptHost extends ScriptHost
                 e.remove();
             }
         }
-
+        if (this.saveTimeout > 0)
+            dumpState();
+        super.onClose();
     }
 
     private void dumpState()
diff --git a/src/main/java/carpet/script/CarpetScriptServer.java b/src/main/java/carpet/script/CarpetScriptServer.java
index 0364945e..34c206c4 100644
--- a/src/main/java/carpet/script/CarpetScriptServer.java
+++ b/src/main/java/carpet/script/CarpetScriptServer.java
@@ -1,14 +1,15 @@
 package carpet.script;
 
 import carpet.script.bundled.BundledModule;
-import carpet.script.value.FunctionValue;
-import carpet.script.value.MapValue;
-import carpet.script.value.StringValue;
 import carpet.CarpetSettings;
 import carpet.CarpetServer;
 import carpet.script.bundled.FileModule;
 import carpet.script.bundled.Module;
 import carpet.script.exception.InvalidCallbackException;
+import carpet.script.value.FunctionValue;
+import carpet.script.value.MapValue;
+import carpet.script.value.StringValue;
+import carpet.script.value.ThreadValue;
 import carpet.script.value.Value;
 import carpet.utils.Messenger;
 import com.mojang.brigadier.arguments.StringArgumentType;
@@ -299,5 +300,6 @@ public class CarpetScriptServer
         {
             host.onClose();
         }
+        ThreadValue.shutdown();
     }
 }
diff --git a/src/main/java/carpet/script/Expression.java b/src/main/java/carpet/script/Expression.java
index b6be4cbf..eeed2959 100644
--- a/src/main/java/carpet/script/Expression.java
+++ b/src/main/java/carpet/script/Expression.java
@@ -2681,6 +2681,10 @@ public class Expression
      * <h3><code>task_completed(task)</code></h3>
      * <p>Returns true if task has completed, or false otherwise.</p>
      *
+     * <h3><code>synchronize(lock, expression)</code></h3>
+     * <p>Evaluates <code>expression</code> synchronized with respect to the lock <code>lock</code>. Returns the value of the
+     * expression.</p>
+     *
      * <hr>
      * <h2>Auxiliary functions</h2>
      *
@@ -3118,6 +3122,23 @@ public class Expression
             return new NumericValue(((ThreadValue) v).isFinished());
         });
 
+        addLazyFunction("synchronize", -1, (c, t, lv) ->
+        {
+            if (lv.size() == 0) throw new InternalExpressionException("'synchronize' require at least an expression to synchronize");
+            Value lockValue = Value.NULL;
+            int ind = 0;
+            if (lv.size() == 2)
+            {
+                lockValue = lv.get(0).evalValue(c);
+                ind = 1;
+            }
+            synchronized (ThreadValue.getLock(lockValue))
+            {
+                Value ret = lv.get(ind).evalValue(c, t);
+                return (_c, _t) -> ret;
+            }
+        });
+
         addLazyFunction("system_variable_get", -1, (c, t, lv) ->
         {
             if (lv.size() == 0) throw new InternalExpressionException("'system_variable_get' expects at least a key to be fetched");
diff --git a/src/main/java/carpet/script/value/ThreadValue.java b/src/main/java/carpet/script/value/ThreadValue.java
index 42682197..6d3998f6 100644
--- a/src/main/java/carpet/script/value/ThreadValue.java
+++ b/src/main/java/carpet/script/value/ThreadValue.java
@@ -10,9 +10,12 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
 
 public class ThreadValue extends Value
 {
@@ -20,6 +23,7 @@ public class ThreadValue extends Value
     private long id;
     private static long sequence = 0L;
     private static final Map<Value,ThreadPoolExecutor> executorServices = new HashMap<>();
+    private static final Map<Value, Object> locks = new ConcurrentHashMap<>();
 
     public ThreadValue(Value pool, FunctionValue function, Expression expr, Tokenizer.Token token, Context ctx, List<LazyValue> args)
     {
@@ -100,4 +104,32 @@ public class ThreadValue extends Value
         }
         return 0;
     }
+
+    public static Object getLock(Value name)
+    {
+        return locks.computeIfAbsent(name, (n) -> new Object());
+    }
+
+
+    public static void shutdown()
+    {
+        for (ExecutorService exec : executorServices.values())
+        {
+            exec.shutdown();
+            try
+            {
+                exec.awaitTermination(5000, TimeUnit.MILLISECONDS);
+            }
+            catch (InterruptedException ignored)
+            {
+            }
+            finally
+            {
+                exec.shutdownNow();
+            }
+        }
+        executorServices.clear();
+        locks.clear();
+    }
+
 }