diff --git a/src/http/ngx_http_upstream.h b/src/http/ngx_http_upstream.h
index 8395362..a7a9a63 100644
--- a/src/http/ngx_http_upstream.h
+++ b/src/http/ngx_http_upstream.h
@@ -269,6 +269,9 @@
 void ngx_http_upstream_init(ngx_http_request_t *r);
 ngx_http_upstream_srv_conf_t *ngx_http_upstream_add(ngx_conf_t *cf,
     ngx_url_t *u, ngx_uint_t flags);
+ngx_int_t ngx_http_upstream_hide_headers_hash(ngx_conf_t *cf,
+    ngx_http_upstream_conf_t *conf, ngx_http_upstream_conf_t *prev,
+    ngx_str_t *default_hide_headers, ngx_hash_init_t *hash);
 
 
 #define ngx_http_conf_upstream_srv_conf(uscf, module)                         \