Block in assert_valid_keys Unknown key: extend (ArgumentError). How to extend the scope?

I'm upgrading a Rails 3 application to Rails 4 and getting the error message

block in assert_valid_keys': Unknown key: extend (ArgumentError)

It appears that extend has been removed in Rails 4 and replaced with extending, which must be included as part of the scope rather than included in the options hash as in prior versions.

In Rails 3 we have a plugin that uses a custom extension module. This was handled in the plugin by adding extend with the module to the options parameter from the plugin which is pretty straight forward since it was just appending to a hash.

Now I need to add extending with the module as part of the scope, but scope will already exist for some modules, so I'm not sure how I can nest or combine these scopes?