How do I use .html.erb as a file extension for my views with Sinatra?

If I have the following Sinatra code:

get '/hi' do
  erb :hello
end

This works great if I have a file called views/hello.erb. However if I have a file called views/hello.html.erb Sinatra can't find the file and gives me an error. How do I tell Sinatra I want it to look for .html.erb as a valid .erb extension?