diff --git a/src/stream/ngx_stream_proxy_module.c b/src/stream/ngx_stream_proxy_module.c
index 0afde1c40..395e0f650 100644
--- a/src/stream/ngx_stream_proxy_module.c
+++ b/src/stream/ngx_stream_proxy_module.c
@@ -1665,13 +1665,17 @@ ngx_stream_proxy_next_upstream(ngx_stream_session_t *s)
     u = s->upstream;
     pc = u->peer.connection;
 
-    if (u->upstream_out || u->upstream_busy || (pc && pc->buffered)) {
+    if (pc && pc->buffered) {
         ngx_log_error(NGX_LOG_ERR, s->connection->log, 0,
-                      "pending buffers on next upstream");
+                      "buffered data on next upstream");
         ngx_stream_proxy_finalize(s, NGX_STREAM_INTERNAL_SERVER_ERROR);
         return;
     }
 
+    if (s->connection->type == SOCK_DGRAM) {
+        u->upstream_out = NULL;
+    }
+
     if (u->peer.sockaddr) {
         u->peer.free(&u->peer, u->peer.data, NGX_PEER_FAILED);
         u->peer.sockaddr = NULL;