Index: /home/dev/workspace/http11/src/java/org/apache/coyote/http11/Http11AprProcessor.java
===================================================================
--- /home/dev/workspace/http11/src/java/org/apache/coyote/http11/Http11AprProcessor.java	(revision 412449)
+++ /home/dev/workspace/http11/src/java/org/apache/coyote/http11/Http11AprProcessor.java	(working copy)
@@ -1613,8 +1613,20 @@
         if (useCompression) {
             outputBuffer.addActiveFilter(outputFilters[Constants.GZIP_FILTER]);
             headers.setValue("Content-Encoding").setString("gzip");
-            // Make Proxies happy via Vary (from mod_deflate)
-            headers.setValue("Vary").setString("Accept-Encoding");
+            
+            // Either add a "Vary: Accept-Encoding" header or add Accept-Encoding to
+            // the existing header.
+            String varyHeaderValue = "";
+            MessageBytes varyHeaderValueBytes = headers.getValue("Vary");
+            if (varyHeaderValueBytes!=null && varyHeaderValueBytes.getString()!=null) {
+            	varyHeaderValue = varyHeaderValueBytes.getString();
+            }
+            if ("".equals(varyHeaderValue)) {
+            	varyHeaderValue="Accept-Encoding";
+            } else {
+            	varyHeaderValue=varyHeaderValue+","+"Accept-Encoding";
+            }
+            headers.setValue("Vary").setString(varyHeaderValue);
         }
 
         // Add date header