diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index 59c9f5f7..c7400e88 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -586,7 +586,8 @@ bool Downstream::request_buf_full() {
 
   if (dconn_) {
     auto &downstreamconf = *worker->get_downstream_config();
-    return request_buf_.rleft() >= downstreamconf.request_buffer_size;
+    return blocked_request_buf_.rleft() + request_buf_.rleft() >=
+           downstreamconf.request_buffer_size;
   }
 
   return false;