Index: modules/filters/mod_deflate.c
===================================================================
--- modules/filters/mod_deflate.c	(revision 687729)
+++ modules/filters/mod_deflate.c	(working copy)
@@ -43,6 +43,7 @@
 #include "util_filter.h"
 #include "apr_buckets.h"
 #include "http_request.h"
+#include "http_protocol.h"
 #define APR_WANT_STRFUNC
 #include "apr_want.h"
 
@@ -537,6 +538,10 @@
         /* For a 304 or 204 response there is no entity included in
          * the response and hence nothing to deflate. */
         if (r->status == HTTP_NOT_MODIFIED || r->status == HTTP_NO_CONTENT) {
+            /* munge the etag only if we had done that when we came in.*/
+            if(apr_table_get(r->notes, "If-None-Match") != NULL)
+                deflate_check_etag(r, "gzip");
+
             ap_remove_output_filter(f);
             return ap_pass_brigade(f->next, bb);
         }
@@ -1329,6 +1334,31 @@
     return APR_SUCCESS;
 }
 
+static int etag_post_read_request(request_rec *r)
+{
+    /* Do not disturb clients who aren't interested in gzip
+    */
+    char* inm;
+    char* gz;
+    const char* accept = apr_table_get(r->headers_in, "Accept-Encoding");
+    if ((accept == NULL) || (ap_strstr_c(accept, "gzip") == NULL)) {
+        return DECLINED;
+    }
+
+    /* Do they have a gzip version?
+    */
+    inm = apr_table_get(r->headers_in, "If-None-Match");
+    if ((inm == NULL) || ( (gz = ap_strstr(inm, "-gzip")) == NULL )) {
+        return DECLINED;
+    }
+
+    *gz = '\0';
+    apr_table_set(r->headers_in, "If-None-Match", apr_pstrdup(r->pool, inm));
+    apr_table_setn(r->notes, "If-None-Match", "1");
+
+    return DECLINED;
+}
+
 #define PROTO_FLAGS AP_FILTER_PROTO_CHANGE|AP_FILTER_PROTO_CHANGE_LENGTH
 static void register_hooks(apr_pool_t *p)
 {
@@ -1338,6 +1368,9 @@
                               AP_FTYPE_RESOURCE-1);
     ap_register_input_filter(deflateFilterName, deflate_in_filter, NULL,
                               AP_FTYPE_CONTENT_SET);
+    ap_hook_post_read_request(etag_post_read_request, NULL, NULL,
+                              APR_HOOK_MIDDLE);
+
 }
 
 static const command_rec deflate_filter_cmds[] = {