diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 5caad00..8ca24e2 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -1394,6 +1394,7 @@
     if (u->cachable) {
         p->temp_file->persistent = 1;
     } else {
+        p->temp_file->log_level = NGX_LOG_WARN;
         p->temp_file->warn = "an upstream response is buffered "
                              "to a temporary file";
     }