diff --git a/apisix/plugins/brotli.lua b/apisix/plugins/brotli.lua
index 031bd8ea9fd3..8a24be7ee068 100644
--- a/apisix/plugins/brotli.lua
+++ b/apisix/plugins/brotli.lua
@@ -222,8 +222,8 @@ function _M.header_filter(conf, ctx)
 
     ctx.brotli_matched = true
     ctx.compressor = compressor
-    core.response.clear_header_as_body_modified()
-    core.response.add_header("Content-Encoding", "br")
+    ngx.header.content_length = nil
+    ngx.header.content_encoding = 'br'
 end