diff --git a/river/src/main/java/org/jboss/marshalling/river/RiverMarshaller.java b/river/src/main/java/org/jboss/marshalling/river/RiverMarshaller.java
index 9f19cacc..746f59aa 100644
--- a/river/src/main/java/org/jboss/marshalling/river/RiverMarshaller.java
+++ b/river/src/main/java/org/jboss/marshalling/river/RiverMarshaller.java
@@ -1481,7 +1481,12 @@ protected void writeNewSerializableClass(final Class<?> objClass) throws IOExcep
             } else {
                 write(ID_SERIALIZABLE_CLASS);
             }
-            writeString(classResolver.getClassName(objClass));
+            final String className = classResolver.getClassName(objClass);
+            if (configuredVersion >= 4) {
+                writeObject(className);
+            } else {
+                writeString(className);
+            }
             writeLong(info.getEffectiveSerialVersionUID());
             classCache.put(objClass, classSeq++);
             classResolver.annotateClass(this, objClass);
@@ -1490,7 +1495,11 @@ protected void writeNewSerializableClass(final Class<?> objClass) throws IOExcep
             writeInt(cnt);
             for (int i = 0; i < cnt; i++) {
                 SerializableField field = fields[i];
-                writeUTF(field.getName());
+                if (configuredVersion >= 4) {
+                    writeObject(field.getName());
+                } else {
+                    writeUTF(field.getName());
+                }
                 try {
                     writeClass(field.getKind() == Kind.OBJECT ? Object.class : field.getType());
                 } catch (ClassNotFoundException e) {
diff --git a/river/src/main/java/org/jboss/marshalling/river/RiverUnmarshaller.java b/river/src/main/java/org/jboss/marshalling/river/RiverUnmarshaller.java
index a5026eba..029b8776 100644
--- a/river/src/main/java/org/jboss/marshalling/river/RiverUnmarshaller.java
+++ b/river/src/main/java/org/jboss/marshalling/river/RiverUnmarshaller.java
@@ -1018,7 +1018,7 @@ ClassDescriptor doReadClassDescriptor(final int classType, final boolean require
             case ID_SERIALIZABLE_CLASS: {
                 int idx = classCache.size();
                 classCache.add(null);
-                final String className = readString();
+                final String className = configuredVersion >= 4 ? readObject(String.class) : readString();
                 final long uid = readLong();
                 Class<?> clazz = null;
                 try {
@@ -1033,7 +1033,7 @@ ClassDescriptor doReadClassDescriptor(final int classType, final boolean require
                 final ClassDescriptor[] descriptors = new ClassDescriptor[cnt];
                 final boolean[] unshareds = new boolean[cnt];
                 for (int i = 0; i < cnt; i ++) {
-                    names[i] = readUTF();
+                    names[i] = configuredVersion >= 4 ? readObject(String.class) : readUTF();
                     descriptors[i] = doReadClassDescriptor(readUnsignedByte(), true);
                     unshareds[i] = readBoolean();
                 }