Index: /apps/workspaces/main/xstream/src/java/com/thoughtworks/xstream/XStream.java
===================================================================
--- /apps/workspaces/main/xstream/src/java/com/thoughtworks/xstream/XStream.java	(revision 719)
+++ /apps/workspaces/main/xstream/src/java/com/thoughtworks/xstream/XStream.java	(working copy)
@@ -97,6 +97,7 @@
 import com.thoughtworks.xstream.io.HierarchicalStreamDriver;
 import com.thoughtworks.xstream.io.HierarchicalStreamReader;
 import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
+import com.thoughtworks.xstream.io.StreamException;
 import com.thoughtworks.xstream.io.xml.PrettyPrintWriter;
 import com.thoughtworks.xstream.io.xml.XppDriver;
 import com.thoughtworks.xstream.mapper.ArrayMapper;
@@ -873,7 +874,11 @@
     public ObjectOutputStream createObjectOutputStream(final HierarchicalStreamWriter writer, String rootNodeName) throws IOException {
         writer.startNode(rootNodeName);
         return new CustomObjectOutputStream(new CustomObjectOutputStream.StreamCallback() {
+        	private boolean closed;
             public void writeToStream(Object object) {
+            	if(closed) {
+            		throw new StreamException("Object output stream was already closed");
+            	}
                 marshal(object, writer);
             }
 
@@ -886,12 +891,18 @@
             }
 
             public void flush() {
-                writer.flush();
+            	if(closed) {
+            		throw new StreamException("Object output stream was already closed");
+            	}
+           		writer.flush();
             }
 
             public void close() {
-                writer.endNode();
-                writer.close();
+            	if(!this.closed) {
+                    writer.endNode();
+                    writer.close();
+                    this.closed = true;
+            	}
             }
         });
     }
Index: /apps/workspaces/main/xstream/src/java/com/thoughtworks/xstream/io/StreamException.java
===================================================================
--- /apps/workspaces/main/xstream/src/java/com/thoughtworks/xstream/io/StreamException.java	(revision 719)
+++ /apps/workspaces/main/xstream/src/java/com/thoughtworks/xstream/io/StreamException.java	(working copy)
@@ -6,4 +6,8 @@
     public StreamException(Throwable e) {
         super(e);
     }
+
+	public StreamException(String message) {
+		super(message);
+	}
 }
Index: /apps/workspaces/main/xstream/src/test/com/thoughtworks/xstream/XStreamTest.java
===================================================================
--- /apps/workspaces/main/xstream/src/test/com/thoughtworks/xstream/XStreamTest.java	(revision 719)
+++ /apps/workspaces/main/xstream/src/test/com/thoughtworks/xstream/XStreamTest.java	(working copy)
@@ -1,5 +1,13 @@
 package com.thoughtworks.xstream;
 
+import java.io.ObjectOutputStream;
+import java.io.StringReader;
+import java.io.StringWriter;
+
+import junit.framework.TestCase;
+
+import org.dom4j.Element;
+
 import com.thoughtworks.acceptance.StandardObject;
 import com.thoughtworks.acceptance.someobjects.FunnyConstructor;
 import com.thoughtworks.acceptance.someobjects.Handler;
@@ -20,12 +28,6 @@
 import com.thoughtworks.xstream.io.xml.AbstractDocumentReader;
 import com.thoughtworks.xstream.io.xml.Dom4JDriver;
 
-import junit.framework.TestCase;
-
-import org.dom4j.Element;
-
-import java.io.StringReader;
-
 public class XStreamTest extends TestCase {
 
     private transient XStream xstream;
@@ -309,5 +311,52 @@
 
         assertEquals("z", z.field);
     }
+    
+    public void testMultipleClose() {
+    	try {
+    		ObjectOutputStream oout = xstream.createObjectOutputStream( new StringWriter() );
+    		oout.writeObject( new Integer( 1 ) );
+    		oout.close();
+    		oout.close();
+        } catch( Exception ex ) {
+        	ex.printStackTrace();
+        	fail( ex.toString() );
+        }
+    }
+
+    public void testObjectOutputStreamCloseTwice() {
+    	try {
+    		ObjectOutputStream oout = xstream.createObjectOutputStream( new StringWriter() );
+    		oout.writeObject( new Integer( 1 ) );
+    		oout.close();
+    		oout.close();
+        } catch( Exception ex ) {
+        	ex.printStackTrace();
+        	fail( ex.toString() );
+        }
+    }
+
+    public void testObjectOutputStreamCloseAndFlush() {
+    	try {
+    		ObjectOutputStream oout = xstream.createObjectOutputStream( new StringWriter() );
+    		oout.writeObject( new Integer( 1 ) );
+    		oout.close();
+    		oout.flush();
+        	fail( "Closing and flushing should throw an IOException" );
+        } catch( Exception ex ) {
+        }
+    }
+
+    public void testObjectOutputStreamCloseAndWrite() {
+    	try {
+    		ObjectOutputStream oout = xstream.createObjectOutputStream( new StringWriter() );
+    		oout.writeObject( new Integer( 1 ) );
+    		oout.close();
+    		oout.writeObject( new Integer( 2 ) );
+        	fail( "Closing and writing should throw an IOException" );
+        } catch( Exception ex ) {
+        }
+    }
 
+
 }