Index: java/org/apache/catalina/connector/Request.java
===================================================================
--- java/org/apache/catalina/connector/Request.java	(revision 929332)
+++ java/org/apache/catalina/connector/Request.java	(working copy)
@@ -2280,10 +2280,11 @@
                         SessionTrackingMode.COOKIE))
             return;
         
-        if (response != null) {
+        if (response != null && !response.isCommitted()) {
             Cookie newCookie =
                 ApplicationSessionCookieConfig.createSessionCookie(context,
                         newSessionId, secure);
+            response.removeCookieInternal(newCookie.getName());
             response.addCookieInternal(newCookie);
         }
     }
Index: java/org/apache/catalina/connector/Response.java
===================================================================
--- java/org/apache/catalina/connector/Response.java	(revision 929332)
+++ java/org/apache/catalina/connector/Response.java	(working copy)
@@ -31,6 +31,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Enumeration;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Locale;
 import java.util.TimeZone;
@@ -1014,6 +1015,49 @@
 
 
     /**
+     * Removes all cookies with the given name from the response.
+     *  
+     * @param cookieName
+     */
+    protected void removeCookieInternal(String cookieName) {
+        
+        if (isCommitted())
+            return;
+        
+        boolean headersToRemove = false;
+        
+        // Remove any cookies from the cookies array 
+        Iterator<Cookie> cookieIter = cookies.iterator();
+        while (cookieIter.hasNext()) {
+            Cookie cookie = cookieIter.next();
+            if (cookieName.equals(cookie.getName())) {
+                cookieIter.remove();
+                headersToRemove = true;
+            }
+        }
+        
+        // Only scan the headers if we have to
+        if (headersToRemove) {
+            String match = cookieName + "=";
+            MimeHeaders headers = coyoteResponse.getMimeHeaders();
+            int i = 0;
+            while (i > -1) {
+                i = headers.findHeader("Set-Cookie", i);
+                if (i > -1) {
+                    if (headers.getValue(i).startsWith(match)) {
+                        // Remove this header.
+                        // Continue search at same position 
+                        headers.removeHeader(i);
+                    } else {
+                        // Continue search at next header
+                        i++;
+                    }
+                }
+            }
+        }
+    }
+    
+    /**
      * Add the specified date header to the specified value.
      *
      * @param name Name of the header to set
Index: java/org/apache/tomcat/util/http/MimeHeaders.java
===================================================================
--- java/org/apache/tomcat/util/http/MimeHeaders.java	(revision 929332)
+++ java/org/apache/tomcat/util/http/MimeHeaders.java	(working copy)
@@ -341,7 +341,7 @@
      * reset and swap with last header
      * @param idx the index of the header to remove.
      */
-    private void removeHeader(int idx) {
+    public void removeHeader(int idx) {
         MimeHeaderField mh = headers[idx];
         
         mh.recycle();