--- src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFWorkbook.java	(revision 1592771)
+++ src/ooxml/java/org/apache/poi/xssf/usermodel/XSSFWorkbook.java	(working copy)
@@ -1307,7 +1307,18 @@ 
                 i++;
             }
             names.setDefinedNameArray(nr);
+            if(workbook.isSetDefinedNames()) {
+                workbook.unsetDefinedNames();
+            }
             workbook.setDefinedNames(names);
+            
+            // Re-process the named ranges
+            namedRanges = new ArrayList<XSSFName>();
+            if(workbook.isSetDefinedNames()) {
+                for(CTDefinedName ctName : workbook.getDefinedNames().getDefinedNameArray()) {
+                    namedRanges.add(new XSSFName(ctName, this));
+                }
+            }
         } else {
             if(workbook.isSetDefinedNames()) {
                 workbook.unsetDefinedNames();
--- src/ooxml/testcases/org/apache/poi/xssf/usermodel/TestMultipleWrites.java	(revision 0)
+++ src/ooxml/testcases/org/apache/poi/xssf/usermodel/TestMultipleWrites.java	(working copy)
@@ -0,0 +1,77 @@ 
+/* ====================================================================
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements.  See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You 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 org.apache.poi.xssf.usermodel;
+
+import static org.junit.Assert.assertEquals;
+import org.junit.Test;
+import java.io.BufferedReader;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import junit.framework.TestCase;
+
+import org.apache.poi.ss.util.CellRangeAddress;
+import org.apache.poi.xssf.usermodel.*;
+
+public class TestMultipleWrites extends TestCase
+{
+    // Assert that multiple writes of a workbook output the same result.
+    public void testMultipleWritesResultInSameWorkbookWritten() throws Exception {
+        XSSFWorkbook wb = new XSSFWorkbook();
+        XSSFSheet sheet = wb.createSheet();
+        XSSFRow row = sheet.createRow(0);
+        XSSFCell cell = row.createCell(0);
+        cell.setCellValue("Hi");
+        
+        // Ensure an entry for the XSSFName collection so that is tested too.
+        sheet.setRepeatingRows(new CellRangeAddress(0, 0, 0, 0));
+
+        ByteArrayOutputStream baos = null;
+        ByteArrayOutputStream baos2 = null;
+        InputStream is = null;
+        InputStream is2 = null;
+        try {
+            baos = new ByteArrayOutputStream(8192);
+            wb.write(baos);
+            is = new ByteArrayInputStream(baos.toByteArray());
+
+            baos2 = new ByteArrayOutputStream(8192);
+            wb.write(baos2);
+            is2 = new ByteArrayInputStream(baos2.toByteArray());
+            
+            // Files are the same size
+            assertEquals(baos.size(), baos2.size());
+            
+            // Files are a binary match
+            int i1;
+            int i2;
+            while (((i1 = is.read()) != -1)&&((i2 = is2.read()) != -1)) {
+                assertEquals(i1, i2);
+            }
+        }
+        finally {
+            if(baos!=null)
+                baos.close();
+            if(baos2!=null)
+                baos2.close();
+            if(is!=null)
+                is.close();
+            if(is2!=null)
+                is2.close();
+        }
+    }
+}