diff --git a/lib/hotwire/spark/middleware.rb b/lib/hotwire/spark/middleware.rb
index a80961c..5000bd6 100644
--- a/lib/hotwire/spark/middleware.rb
+++ b/lib/hotwire/spark/middleware.rb
@@ -12,7 +12,7 @@ def call(env)
       html = html_from(response)
       html = inject_options(html)
       html = inject_javascript(html)
-      headers["Content-Length"] = html.bytesize.to_s if html
+      headers.delete("Content-Length")
       response = [ html ]
     end