diff --git a/src/ngx_http_lua_balancer.c b/src/ngx_http_lua_balancer.c
index e37177d4fe..ae0f1380b5 100644
--- a/src/ngx_http_lua_balancer.c
+++ b/src/ngx_http_lua_balancer.c
@@ -860,8 +860,8 @@ ngx_http_lua_balancer_save_session(ngx_peer_connection_t *pc, void *data)
 int
 ngx_http_lua_ffi_balancer_set_current_peer(ngx_http_request_t *r,
     const u_char *addr, size_t addr_len, int port,
-    char **err,
-    const u_char *host, size_t host_len)
+    const u_char *host, size_t host_len,
+    char **err)
 {
     ngx_url_t              url;
     ngx_http_lua_ctx_t    *ctx;