diff --git a/config/initializers/mime_types.rb b/config/initializers/mime_types.rb
index 6233e74..7219fad 100644
--- a/config/initializers/mime_types.rb
+++ b/config/initializers/mime_types.rb
@@ -3,4 +3,4 @@
 # Add new mime types for use in respond_to blocks:
 # Mime::Type.register "text/richtext", :rtf
 
-Mime::Type.register "text/javascript", :mjs, %w( application/javascript application/x-javascript )
+Rack::Mime::MIME_TYPES[".mjs"] = "text/javascript"