diff --git a/src/event/ngx_event_pipe.c b/src/event/ngx_event_pipe.c
index be1b475bb..f54e07005 100644
--- a/src/event/ngx_event_pipe.c
+++ b/src/event/ngx_event_pipe.c
@@ -113,11 +113,24 @@ ngx_event_pipe_read_upstream(ngx_event_pipe_t *p)
     }
 
 #if (NGX_THREADS)
+
     if (p->aio) {
         ngx_log_debug0(NGX_LOG_DEBUG_EVENT, p->log, 0,
                        "pipe read upstream: aio");
         return NGX_AGAIN;
     }
+
+    if (p->writing) {
+        ngx_log_debug0(NGX_LOG_DEBUG_EVENT, p->log, 0,
+                       "pipe read upstream: writing");
+
+        rc = ngx_event_pipe_write_chain_to_temp_file(p);
+
+        if (rc != NGX_OK) {
+            return rc;
+        }
+    }
+
 #endif
 
     ngx_log_debug1(NGX_LOG_DEBUG_EVENT, p->log, 0,
diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
index 1386bdb95..168f6b48f 100644
--- a/src/http/ngx_http_upstream.c
+++ b/src/http/ngx_http_upstream.c
@@ -3744,9 +3744,24 @@ ngx_http_upstream_process_request(ngx_http_request_t *r,
     p = u->pipe;
 
 #if (NGX_THREADS)
+
+    if (p->writing && !p->aio) {
+
+        /*
+         * make sure to call ngx_event_pipe()
+         * if there is an incomplete aio write
+         */
+
+        if (ngx_event_pipe(p, 1) == NGX_ABORT) {
+            ngx_http_upstream_finalize_request(r, u, NGX_ERROR);
+            return;
+        }
+    }
+
     if (p->writing) {
         return;
     }
+
 #endif
 
     if (u->peer.connection) {