diff --git a/lib/flipper/ui/actions/file.rb b/lib/flipper/ui/actions/file.rb
index 7a8089515..4ed0a5a34 100644
--- a/lib/flipper/ui/actions/file.rb
+++ b/lib/flipper/ui/actions/file.rb
@@ -1,4 +1,8 @@
-require 'rack/file'
+if Rack.release >= "2.1"
+  require 'rack/files'
+else
+  require 'rack/file'
+end
 require 'flipper/ui/action'
 
 module Flipper
@@ -8,7 +12,8 @@ class File < UI::Action
         route %r{(images|css|js)/.*\Z}
 
         def get
-          Rack::File.new(public_path).call(request.env)
+          klass = Rack.release >= "2.1" ? Rack::Files : Rack::File
+          klass.new(public_path).call(request.env)
         end
       end
     end