--- a/src/http/modules/ngx_http_gzip_filter_module.c
+++ b/src/http/modules/ngx_http_gzip_filter_module.c
@@ -246,17 +246,27 @@ ngx_http_gzip_header_filter(ngx_http_req
         || (r->headers_out.status != NGX_HTTP_OK
             && r->headers_out.status != NGX_HTTP_FORBIDDEN
             && r->headers_out.status != NGX_HTTP_NOT_FOUND)
-        || r->header_only
         || (r->headers_out.content_encoding
             && r->headers_out.content_encoding->value.len)
         || (r->headers_out.content_length_n != -1
             && r->headers_out.content_length_n < conf->min_length)
         || ngx_http_test_content_type(r, &conf->types) == NULL
-        || ngx_http_gzip_ok(r) != NGX_OK)
+        || r->header_only)
     {
         return ngx_http_next_header_filter(r);
     }
 
+    r->gzip_vary = 1;
+
+    if (!r->gzip_tested) {
+        if (ngx_http_gzip_ok(r) != NGX_OK) {
+            return ngx_http_next_header_filter(r);
+        }
+
+    } else if (!r->gzip_ok) {
+        return ngx_http_next_header_filter(r);
+    }
+
     ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_gzip_ctx_t));
     if (ctx == NULL) {
         return NGX_ERROR;
@@ -1113,8 +1123,8 @@ ngx_http_gzip_merge_conf(ngx_conf_t *cf,
                               MAX_MEM_LEVEL - 1);
     ngx_conf_merge_value(conf->min_length, prev->min_length, 20);
 
-    if (ngx_http_merge_types(cf, conf->types_keys, &conf->types,
-                             prev->types_keys, &prev->types,
+    if (ngx_http_merge_types(cf, &conf->types_keys, &conf->types,
+                             &prev->types_keys, &prev->types,
                              ngx_http_html_default_types)
         != NGX_OK)
     {