--- a/src/http/ngx_http_core_module.c	Wed Mar 15 19:57:15 2023 +0400
+++ b/src/http/ngx_http_core_module.c	Wed Mar 29 11:14:25 2023 +0400
@@ -1803,10 +1803,6 @@
         }
     }
 
-    if (r != r->main && val.len == 0) {
-        return ngx_http_send_header(r);
-    }
-
     b = ngx_calloc_buf(r->pool);
     if (b == NULL) {
         return NGX_HTTP_INTERNAL_SERVER_ERROR;
@@ -1817,6 +1813,7 @@
     b->memory = val.len ? 1 : 0;
     b->last_buf = (r == r->main) ? 1 : 0;
     b->last_in_chain = 1;
+    b->sync = (b->last_buf || b->memory) ? 0 : 1;
 
     out.buf = b;
     out.next = NULL;