diff --git a/pom.xml b/pom.xml
index c7e64009f..bb883ecb1 100755
--- a/pom.xml
+++ b/pom.xml
@@ -44,7 +44,7 @@
             <dependency>
                 <groupId>net.openhft</groupId>
                 <artifactId>lang</artifactId>
-                <version>6.4.9</version>
+                <version>6.4.10-SNAPSHOT</version>
             </dependency>
 
             <dependency>
diff --git a/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java b/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java
index bbcaaa7de..fd3cfdda4 100644
--- a/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java
+++ b/src/main/java/net/openhft/chronicle/map/ChronicleMapBuilder.java
@@ -20,6 +20,7 @@ import net.openhft.chronicle.ChronicleHashBuilder;
 import net.openhft.chronicle.ChronicleHashErrorListener;
 import net.openhft.chronicle.ChronicleHashErrorListeners;
 import net.openhft.chronicle.TimeProvider;
+import net.openhft.chronicle.map.serialization.AgileBytesMarshaller;
 import net.openhft.chronicle.map.serialization.MetaBytesInterop;
 import net.openhft.chronicle.map.serialization.MetaBytesWriter;
 import net.openhft.chronicle.map.serialization.MetaProvider;
@@ -638,6 +639,13 @@ public class ChronicleMapBuilder<K, V> implements Cloneable,
         return this;
     }
 
+    public ChronicleMapBuilder<K, V> valueMarshallerAndFactory(
+            @NotNull AgileBytesMarshaller<V> valueMarshaller,
+            @NotNull ObjectFactory<V> valueFactory) {
+        valueBuilder.agileMarshaller(valueMarshaller, valueFactory);
+        return this;
+    }
+
     public ChronicleMapBuilder<K, V> valueFactory(@NotNull ObjectFactory<V> valueFactory) {
         valueBuilder.factory(valueFactory);
         return this;
diff --git a/src/main/java/net/openhft/chronicle/map/SerializationBuilder.java b/src/main/java/net/openhft/chronicle/map/SerializationBuilder.java
index c55306fd3..4973970bb 100644
--- a/src/main/java/net/openhft/chronicle/map/SerializationBuilder.java
+++ b/src/main/java/net/openhft/chronicle/map/SerializationBuilder.java
@@ -80,7 +80,7 @@ final class SerializationBuilder<E> implements Cloneable {
         if (role == Role.VALUE) {
             factory = concreteClass(eClass) && marshallerUseFactory(eClass) ?
                     new NewInstanceObjectFactory<E>(eClass) :
-                    NullObjectFactory.INSTANCE;
+                    NullObjectFactory.of();
         }
 
         if (concreteClass(eClass) && Byteable.class.isAssignableFrom(eClass)) {
diff --git a/src/main/java/net/openhft/chronicle/set/ChronicleSetBuilder.java b/src/main/java/net/openhft/chronicle/set/ChronicleSetBuilder.java
index 26a27f8f5..5473edcb5 100644
--- a/src/main/java/net/openhft/chronicle/set/ChronicleSetBuilder.java
+++ b/src/main/java/net/openhft/chronicle/set/ChronicleSetBuilder.java
@@ -16,35 +16,30 @@
 
 package net.openhft.chronicle.set;
 
-import net.openhft.chronicle.TimeProvider;
-import net.openhft.chronicle.map.Alignment;
 import net.openhft.chronicle.ChronicleHashBuilder;
 import net.openhft.chronicle.ChronicleHashErrorListener;
+import net.openhft.chronicle.TimeProvider;
 import net.openhft.chronicle.map.*;
 import net.openhft.lang.io.serialization.BytesMarshaller;
 import net.openhft.lang.io.serialization.BytesMarshallerFactory;
 import net.openhft.lang.io.serialization.ObjectSerializer;
+import net.openhft.lang.io.serialization.impl.NullObjectFactory;
 import org.jetbrains.annotations.NotNull;
 
 import java.io.File;
 import java.io.IOException;
-import java.io.Serializable;
-import java.util.AbstractSet;
-import java.util.Collection;
-import java.util.Iterator;
-import java.util.Set;
-import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.TimeUnit;
 
 
 public class ChronicleSetBuilder<E>
         implements ChronicleHashBuilder<E, ChronicleSet<E>, ChronicleSetBuilder<E>> {
 
-    private ChronicleMapBuilder<E, Void> chronicleMapBuilder;
+    private ChronicleMapBuilder<E, DummyValue> chronicleMapBuilder;
 
     ChronicleSetBuilder(Class<E> keyClass) {
-        chronicleMapBuilder = ChronicleMapBuilder.of(keyClass, Void.class)
-                .entryAndValueAlignment(Alignment.NO_ALIGNMENT);
+        chronicleMapBuilder = ChronicleMapBuilder.of(keyClass, DummyValue.class)
+                .entryAndValueAlignment(Alignment.NO_ALIGNMENT)
+                .valueMarshallerAndFactory(DummyValueMarshaller.INSTANCE, NullObjectFactory.of());
     }
 
     public static <K> ChronicleSetBuilder<K> of(Class<K> keyClass) {
@@ -229,108 +224,15 @@ public class ChronicleSetBuilder<E>
 
     @Override
     public ChronicleSet<E> create(File file) throws IOException {
-        final ChronicleMap<E, Void> map = chronicleMapBuilder.create(file);
+        final ChronicleMap<E, DummyValue> map = chronicleMapBuilder.create(file);
         return new SetFromMap<E>(map);
     }
 
     @Override
     public ChronicleSet<E> create() throws IOException {
-        final ChronicleMap<E, Void> map = chronicleMapBuilder.create();
+        final ChronicleMap<E, DummyValue> map = chronicleMapBuilder.create();
         return new SetFromMap<E>(map);
     }
 
-    private static class SetFromMap<E> extends AbstractSet<E>
-            implements ChronicleSet<E>, Serializable {
-
-        private final ChronicleMap<E, Void> m;  // The backing map
-        private transient Set<E> s;       // Its keySet
-
-        SetFromMap(ChronicleMap<E, Void> map) {
-            if (!map.isEmpty())
-                throw new IllegalArgumentException("Map is non-empty");
-            m = map;
-            s = map.keySet();
-        }
-
-        public void clear() {
-            m.clear();
-        }
-
-        public int size() {
-            return m.size();
-        }
-
-        public boolean isEmpty() {
-            return m.isEmpty();
-        }
-
-        public boolean contains(Object o) {
-            return m.containsKey(o);
-        }
-
-        public boolean remove(Object o) {
-            return m.remove(o) != null;
-        }
-
-        public boolean add(E e) {
-            return m.put(e, (Void) null) == null;
-        }
-
-        public Iterator<E> iterator() {
-            return s.iterator();
-        }
-
-        public Object[] toArray() {
-            return s.toArray();
-        }
-
-        public <T> T[] toArray(T[] a) {
-            return s.toArray(a);
-        }
-
-        public String toString() {
-            return s.toString();
-        }
-
-        public int hashCode() {
-            return s.hashCode();
-        }
-
-        public boolean equals(Object o) {
-            return o == this || s.equals(o);
-        }
-
-        public boolean containsAll(Collection<?> c) {
-            return s.containsAll(c);
-        }
-
-        public boolean removeAll(Collection<?> c) {
-            return s.removeAll(c);
-        }
-
-        public boolean retainAll(Collection<?> c) {
-            return s.retainAll(c);
-        }
-        // addAll is the only inherited implementation
-
-        private static final long serialVersionUID = 2454657854757543876L;
-
-        private void readObject(java.io.ObjectInputStream stream)
-                throws IOException, ClassNotFoundException {
-            stream.defaultReadObject();
-            s = m.keySet();
-        }
-
-        @Override
-        public long longSize() {
-            return m.longSize();
-        }
-
-        @Override
-        public void close() throws IOException {
-            m.close();
-        }
-    }
-
 }
 
diff --git a/src/main/java/net/openhft/chronicle/set/DummyValue.java b/src/main/java/net/openhft/chronicle/set/DummyValue.java
new file mode 100644
index 000000000..1d73a070b
--- /dev/null
+++ b/src/main/java/net/openhft/chronicle/set/DummyValue.java
@@ -0,0 +1,21 @@
+/*
+ * Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.openhft.chronicle.set;
+
+enum DummyValue {
+    DUMMY_VALUE
+}
diff --git a/src/main/java/net/openhft/chronicle/set/DummyValueMarshaller.java b/src/main/java/net/openhft/chronicle/set/DummyValueMarshaller.java
new file mode 100644
index 000000000..85bb16462
--- /dev/null
+++ b/src/main/java/net/openhft/chronicle/set/DummyValueMarshaller.java
@@ -0,0 +1,71 @@
+/*
+ * Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.openhft.chronicle.set;
+
+import net.openhft.chronicle.map.serialization.AgileBytesMarshaller;
+import net.openhft.lang.io.Bytes;
+
+import static net.openhft.chronicle.set.DummyValue.DUMMY_VALUE;
+
+enum DummyValueMarshaller implements AgileBytesMarshaller<DummyValue> {
+    INSTANCE;
+
+    @Override
+    public boolean startsWith(Bytes bytes, DummyValue dummyValue) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public long hash(DummyValue dummyValue) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public DummyValue read(Bytes bytes, long size) {
+        return DUMMY_VALUE;
+    }
+
+    @Override
+    public DummyValue read(Bytes bytes, long size, DummyValue dummyValue) {
+        return DUMMY_VALUE;
+    }
+
+    @Override
+    public long size(DummyValue dummyValue) {
+        return 0L;
+    }
+
+    @Override
+    public void write(Bytes bytes, DummyValue dummyValue) {
+        // do nothing
+    }
+
+    @Override
+    public int sizeEncodingSize(long size) {
+        return 0;
+    }
+
+    @Override
+    public void writeSize(Bytes bytes, long size) {
+        // do nothing
+    }
+
+    @Override
+    public long readSize(Bytes bytes) {
+        return 0L;
+    }
+}
diff --git a/src/main/java/net/openhft/chronicle/set/SetFromMap.java b/src/main/java/net/openhft/chronicle/set/SetFromMap.java
new file mode 100644
index 000000000..47fd84883
--- /dev/null
+++ b/src/main/java/net/openhft/chronicle/set/SetFromMap.java
@@ -0,0 +1,122 @@
+/*
+ * Copyright 2014 Higher Frequency Trading http://www.higherfrequencytrading.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package net.openhft.chronicle.set;
+
+import net.openhft.chronicle.map.ChronicleMap;
+import net.openhft.chronicle.map.ChronicleSet;
+
+import java.io.IOException;
+import java.io.Serializable;
+import java.util.AbstractSet;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.Set;
+
+import static net.openhft.chronicle.set.DummyValue.DUMMY_VALUE;
+
+class SetFromMap<E> extends AbstractSet<E>
+        implements ChronicleSet<E>, Serializable {
+
+    private final ChronicleMap<E, DummyValue> m;  // The backing map
+    private transient Set<E> s;       // Its keySet
+
+    SetFromMap(ChronicleMap<E, DummyValue> map) {
+        if (!map.isEmpty())
+            throw new IllegalArgumentException("Map is non-empty");
+        m = map;
+        s = map.keySet();
+    }
+
+    public void clear() {
+        m.clear();
+    }
+
+    public int size() {
+        return m.size();
+    }
+
+    public boolean isEmpty() {
+        return m.isEmpty();
+    }
+
+    public boolean contains(Object o) {
+        return m.containsKey(o);
+    }
+
+    public boolean remove(Object o) {
+        return m.remove(o) == DUMMY_VALUE;
+    }
+
+    public boolean add(E e) {
+        return m.putIfAbsent(e, DUMMY_VALUE) == null;
+    }
+
+    public Iterator<E> iterator() {
+        return s.iterator();
+    }
+
+    public Object[] toArray() {
+        return s.toArray();
+    }
+
+    public <T> T[] toArray(T[] a) {
+        return s.toArray(a);
+    }
+
+    public String toString() {
+        return s.toString();
+    }
+
+    public int hashCode() {
+        return s.hashCode();
+    }
+
+    public boolean equals(Object o) {
+        return o == this || s.equals(o);
+    }
+
+    public boolean containsAll(Collection<?> c) {
+        return s.containsAll(c);
+    }
+
+    public boolean removeAll(Collection<?> c) {
+        return s.removeAll(c);
+    }
+
+    public boolean retainAll(Collection<?> c) {
+        return s.retainAll(c);
+    }
+    // addAll is the only inherited implementation
+
+    private static final long serialVersionUID = 2454657854757543876L;
+
+    private void readObject(java.io.ObjectInputStream stream)
+            throws IOException, ClassNotFoundException {
+        stream.defaultReadObject();
+        s = m.keySet();
+    }
+
+    @Override
+    public long longSize() {
+        return m.longSize();
+    }
+
+    @Override
+    public void close() throws IOException {
+        m.close();
+    }
+}