diff --git a/src/main/java/io/vertx/core/impl/ContextImpl.java b/src/main/java/io/vertx/core/impl/ContextImpl.java
index 46b73cc6881..37a0e0d631a 100644
--- a/src/main/java/io/vertx/core/impl/ContextImpl.java
+++ b/src/main/java/io/vertx/core/impl/ContextImpl.java
@@ -17,10 +17,12 @@
 import io.vertx.core.impl.logging.Logger;
 import io.vertx.core.impl.logging.LoggerFactory;
 import io.vertx.core.json.JsonObject;
+import io.vertx.core.spi.context.storage.ContextLocal;
 import io.vertx.core.spi.metrics.PoolMetrics;
 import io.vertx.core.spi.tracing.VertxTracer;
 
 import java.util.concurrent.*;
+import java.util.function.UnaryOperator;
 
 /**
  * A base class for {@link Context} implementations.
diff --git a/src/main/java/io/vertx/core/impl/ContextInternal.java b/src/main/java/io/vertx/core/impl/ContextInternal.java
index 34bd5aa377e..d772e232c27 100644
--- a/src/main/java/io/vertx/core/impl/ContextInternal.java
+++ b/src/main/java/io/vertx/core/impl/ContextInternal.java
@@ -25,6 +25,7 @@
 import java.util.Objects;
 import java.util.concurrent.*;
 import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
 
 /**
  * This interface provides an api for vert.x core internal use only
@@ -35,7 +36,7 @@
  */
 public interface ContextInternal extends Context {
 
-  ContextLocal<ConcurrentMap<Object, Object>> LOCAL_MAP = new ContextLocalImpl<>(0);
+  ContextLocal<ConcurrentMap<Object, Object>> LOCAL_MAP = (ContextLocal) new ContextLocalImpl<>(0, ConcurrentMap.class, t -> new ConcurrentHashMap<>(t));
 
   /**
    * @return the current context
diff --git a/src/main/java/io/vertx/core/impl/ContextLocalImpl.java b/src/main/java/io/vertx/core/impl/ContextLocalImpl.java
index 02671c9a58c..bf9e4810ea0 100644
--- a/src/main/java/io/vertx/core/impl/ContextLocalImpl.java
+++ b/src/main/java/io/vertx/core/impl/ContextLocalImpl.java
@@ -12,18 +12,31 @@
 
 import io.vertx.core.spi.context.storage.ContextLocal;
 
+import java.util.function.Function;
+import java.util.function.UnaryOperator;
+
 /**
  * @author <a href="mailto:julien@julienviet.com">Julien Viet</a>
  */
 public class ContextLocalImpl<T> implements ContextLocal<T> {
 
-  final int index;
+  public static <T> ContextLocal<T> registerLocal(Class<T> type) {
+    return registerLocal(type, (UnaryOperator<T>) ContextLocalImpl.IDENTITY);
+  }
 
-  public ContextLocalImpl(int index) {
-    this.index = index;
+  public static <T> ContextLocal<T> registerLocal(Class<T> type, Function<T, ? extends T> duplicator) {
+    return LocalSeq.add(idx -> new ContextLocalImpl<>(idx, type, duplicator));
   }
 
-  public ContextLocalImpl() {
-    this.index = LocalSeq.next();
+  public static final UnaryOperator<?> IDENTITY = UnaryOperator.identity();
+
+  final int index;
+  final Class<T> type;
+  final  Function<T, ? extends T> duplicator;
+
+  ContextLocalImpl(int index, Class<T> type, Function<T, ? extends T> duplicator) {
+    this.index = index;
+    this.type = type;
+    this.duplicator = duplicator;
   }
 }
diff --git a/src/main/java/io/vertx/core/impl/DuplicatedContext.java b/src/main/java/io/vertx/core/impl/DuplicatedContext.java
index fc2fddfac6d..d142b83f073 100644
--- a/src/main/java/io/vertx/core/impl/DuplicatedContext.java
+++ b/src/main/java/io/vertx/core/impl/DuplicatedContext.java
@@ -16,10 +16,10 @@
 import io.vertx.core.Handler;
 import io.vertx.core.ThreadingModel;
 import io.vertx.core.json.JsonObject;
+import io.vertx.core.spi.context.storage.ContextLocal;
 import io.vertx.core.spi.tracing.VertxTracer;
 
 import java.util.concurrent.Callable;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 import java.util.concurrent.Executor;
 
@@ -164,7 +164,28 @@ public boolean isWorkerContext() {
 
   @Override
   public ContextInternal duplicate() {
-    return new DuplicatedContext(delegate, locals.length == 0 ? VertxImpl.EMPTY_CONTEXT_LOCALS : new Object[locals.length]);
+    Object[] localsDuplicate = locals.length == 0 ? VertxImpl.EMPTY_CONTEXT_LOCALS : locals.clone();
+    ContextLocal<?>[] contextLocals = ((VertxImpl) delegate.owner()).contextLocals;
+    for (int i = 0;i < localsDuplicate.length;i++) {
+      ContextLocalImpl<?> contextLocal = (ContextLocalImpl<?>) contextLocals[i];
+      Object local = locals[i];
+      if (local != null) {
+        if (local != ContextLocalImpl.IDENTITY) {
+          localsDuplicate[i] = duplicate(local, contextLocal);
+        } else {
+          localsDuplicate[i] = local;
+        }
+      }
+    }
+    return new DuplicatedContext(delegate, localsDuplicate);
+  }
+
+  private static <T> T duplicate(Object o, ContextLocalImpl<T> contextLocal) {
+    if (contextLocal.type.isInstance(o)) {
+      return contextLocal.duplicator.apply(contextLocal.type.cast(o));
+    } else {
+      throw new ClassCastException();
+    }
   }
 
   @Override
diff --git a/src/main/java/io/vertx/core/impl/LocalSeq.java b/src/main/java/io/vertx/core/impl/LocalSeq.java
index b9b4a7f0d8a..6a716df250f 100644
--- a/src/main/java/io/vertx/core/impl/LocalSeq.java
+++ b/src/main/java/io/vertx/core/impl/LocalSeq.java
@@ -10,7 +10,11 @@
  */
 package io.vertx.core.impl;
 
-import java.util.concurrent.atomic.AtomicInteger;
+import io.vertx.core.spi.context.storage.ContextLocal;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.IntFunction;
 
 /**
  * @author <a href="mailto:julien@julienviet.com">Julien Viet</a>
@@ -18,20 +22,34 @@
 class LocalSeq {
 
   // 0 : reserved slot for local context map
-  private static final AtomicInteger seq = new AtomicInteger(1);
+  private static final List<ContextLocal<?>> locals = new ArrayList<>();
+
+  static {
+    reset();
+  }
 
   /**
    * Hook for testing purposes
    */
   static void reset() {
-    seq.set((1));
+    synchronized (locals) {
+      locals.clear();
+      locals.add(ContextInternal.LOCAL_MAP);
+    }
   }
 
-  static int get() {
-    return seq.get();
+  static ContextLocal<?>[] get() {
+    synchronized (locals) {
+      return locals.toArray(new ContextLocal[0]);
+    }
   }
 
-  static int next() {
-    return seq.getAndIncrement();
+  static <T> ContextLocal<T> add(IntFunction<ContextLocal<T>> provider) {
+    synchronized (locals) {
+      int idx = locals.size();
+      ContextLocal<T> local = provider.apply(idx);
+      locals.add(local);
+      return local;
+    }
   }
 }
diff --git a/src/main/java/io/vertx/core/impl/VertxImpl.java b/src/main/java/io/vertx/core/impl/VertxImpl.java
index 59734a3d856..86711dc15cb 100644
--- a/src/main/java/io/vertx/core/impl/VertxImpl.java
+++ b/src/main/java/io/vertx/core/impl/VertxImpl.java
@@ -37,6 +37,7 @@
 import io.vertx.core.net.*;
 import io.vertx.core.net.impl.*;
 import io.vertx.core.impl.transports.JDKTransport;
+import io.vertx.core.spi.context.storage.ContextLocal;
 import io.vertx.core.spi.file.FileResolver;
 import io.vertx.core.file.impl.FileSystemImpl;
 import io.vertx.core.file.impl.WindowsFileSystem;
@@ -73,6 +74,7 @@
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
 
 /**
  * @author <a href="http://tfox.org">Tim Fox</a>
@@ -136,7 +138,7 @@ private static ThreadFactory virtualThreadFactory() {
   private final VerticleManager verticleManager;
   private final FileResolver fileResolver;
   private final Map<ServerID, NetServerInternal> sharedNetServers = new HashMap<>();
-  private final int contextLocals;
+  final ContextLocal<?>[] contextLocals;
   final WorkerPool workerPool;
   final WorkerPool internalWorkerPool;
   final WorkerPool virtualThreaWorkerPool;
@@ -503,10 +505,11 @@ public boolean cancelTimer(long id) {
   }
 
   private Object[] createContextLocals() {
-    if (contextLocals == 0) {
+    int len = contextLocals.length;
+    if (len == 0) {
       return EMPTY_CONTEXT_LOCALS;
     } else {
-      return new Object[contextLocals];
+      return new Object[len];
     }
   }
 
diff --git a/src/main/java/io/vertx/core/spi/context/storage/ContextLocal.java b/src/main/java/io/vertx/core/spi/context/storage/ContextLocal.java
index 8831b74098f..6811b8093d0 100644
--- a/src/main/java/io/vertx/core/spi/context/storage/ContextLocal.java
+++ b/src/main/java/io/vertx/core/spi/context/storage/ContextLocal.java
@@ -15,6 +15,7 @@
 import io.vertx.core.impl.ContextLocalImpl;
 
 import java.util.function.Supplier;
+import java.util.function.UnaryOperator;
 
 /**
  * A local storage for arbitrary data attached to a duplicated {@link Context}.
@@ -35,7 +36,16 @@ public interface ContextLocal<T> {
    * @return the context local storage
    */
   static <T> ContextLocal<T> registerLocal(Class<T> type) {
-    return new ContextLocalImpl<>();
+    return ContextLocalImpl.registerLocal(type);
+  }
+
+  /**
+   * Registers a context local storage.
+   *
+   * @return the context local storage
+   */
+  static <T> ContextLocal<T> registerLocal(Class<T> type, UnaryOperator<T> duplicator) {
+    return ContextLocalImpl.registerLocal(type, duplicator);
   }
 
   /**
@@ -58,6 +68,10 @@ default T get(Context context, Supplier<? extends T> initialValueSupplier) {
     return get(context, AccessMode.CONCURRENT, initialValueSupplier);
   }
 
+  default T duplicate(T value) {
+    return  value;
+  }
+
   /**
    * Put local data in the {@code context}.
    *
diff --git a/src/test/java/io/vertx/core/ContextTest.java b/src/test/java/io/vertx/core/ContextTest.java
index c41eb3a087a..2a64f2afb34 100644
--- a/src/test/java/io/vertx/core/ContextTest.java
+++ b/src/test/java/io/vertx/core/ContextTest.java
@@ -1092,4 +1092,18 @@ public void testConcurrentLocalAccess() throws Exception {
     }
   }
 
+  @Test
+  public void testNestedDuplicate() {
+    ContextInternal ctx = ((ContextInternal) vertx.getOrCreateContext()).duplicate();
+    ctx.putLocal("foo", "bar");
+    Object expected = new Object();
+    ctx.putLocal(contextLocal, AccessMode.CONCURRENT, expected);
+    ContextInternal duplicate = ctx.duplicate();
+    assertEquals("bar", duplicate.getLocal("foo"));
+    assertEquals(expected, duplicate.getLocal(contextLocal));
+    ctx.removeLocal("foo");
+    ctx.removeLocal(contextLocal, AccessMode.CONCURRENT);
+    assertEquals("bar", duplicate.getLocal("foo"));
+    assertEquals(expected, duplicate.getLocal(contextLocal));
+  }
 }