diff --git a/src/http/ngx_http_core_module.c b/src/http/ngx_http_core_module.c
index 984d306..1654510 100644
--- a/src/http/ngx_http_core_module.c
+++ b/src/http/ngx_http_core_module.c
@@ -1748,6 +1748,7 @@
     r->headers_out.status = status;
 
     if (status == NGX_HTTP_NO_CONTENT) {
+        r->header_only = 1;
         return ngx_http_send_header(r);
     }
 
diff --git a/src/http/ngx_http_header_filter_module.c b/src/http/ngx_http_header_filter_module.c
index a8687d0..bccf636 100644
--- a/src/http/ngx_http_header_filter_module.c
+++ b/src/http/ngx_http_header_filter_module.c
@@ -170,6 +170,10 @@
 #endif
     u_char                     addr[NGX_SOCKADDR_STRLEN];
 
+    if (r->header_sent) {
+        return NGX_OK;
+    }
+
     r->header_sent = 1;
 
     if (r != r->main) {