--- a/src/http/ngx_http_request.h
+++ b/src/http/ngx_http_request.h
@@ -547,6 +547,7 @@ struct ngx_http_request_s {
     unsigned                          request_complete:1;
     unsigned                          request_output:1;
     unsigned                          header_sent:1;
+    unsigned                          response_sent:1;
     unsigned                          expect_tested:1;
     unsigned                          root_tested:1;
     unsigned                          done:1;

--- a/src/http/ngx_http_write_filter_module.c
+++ b/src/http/ngx_http_write_filter_module.c
@@ -239,6 +239,10 @@ ngx_http_write_filter(ngx_http_request_t
             r->out = NULL;
             c->buffered &= ~NGX_HTTP_WRITE_BUFFERED;
 
+            if (last) {
+                r->response_sent = 1;
+            }
+
             return NGX_OK;
         }
 
@@ -350,6 +354,10 @@ ngx_http_write_filter(ngx_http_request_t
 
     c->buffered &= ~NGX_HTTP_WRITE_BUFFERED;
 
+    if (last) {
+        r->response_sent = 1;
+    }
+
     if ((c->buffered & NGX_LOWLEVEL_BUFFERED) && r->postponed == NULL) {
         return NGX_AGAIN;
     }