diff --git a/CHANGES b/CHANGES
index 8e7682bfa4..e27701d8aa 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,9 @@ Changes with Apache 2.1.0-dev
 
   [Remove entries to the current 2.0 section below, when backported]
 
+  *) Add another check for already compressed content in mod_deflate.
+     PR 19913. [Tsuyoshi SASAMOTO <nazonazo@super.win.ne.jp>]
+
   *) Add a delete flag to htpasswd.
      [Thom May]
 
diff --git a/modules/filters/mod_deflate.c b/modules/filters/mod_deflate.c
index c8d8ae9b0d..1285da8f58 100644
--- a/modules/filters/mod_deflate.c
+++ b/modules/filters/mod_deflate.c
@@ -340,6 +340,12 @@ static apr_status_t deflate_out_filter(ap_filter_t *f,
             encoding = apr_table_get(r->err_headers_out, "Content-Encoding");
         }
 
+        if (r->content_encoding) {
+            encoding = encoding ? apr_pstrcat(r->pool, encoding, ",",
+                                              r->content_encoding, NULL)
+                                : r->content_encoding;
+        }
+
         if (encoding) {
             const char *tmp = encoding;