diff --git a/lib/rackup/handler/cgi.rb b/lib/rackup/handler/cgi.rb
index a8f8a11..d793627 100644
--- a/lib/rackup/handler/cgi.rb
+++ b/lib/rackup/handler/cgi.rb
@@ -40,6 +40,8 @@ def self.serve(app)
       def self.send_headers(status, headers)
         $stdout.print "Status: #{status}\r\n"
         headers.each { |k, vs|
+          next if k.start_with?('rack.')
+
           vs.split("\n").each { |v|
             $stdout.print "#{k}: #{v}\r\n"
           }