How to ignore extra messages with RSpec should_receive?

Spec:

before do
  Logger.should_receive( :write ).with 'Log message 1'    
end

it 'works' do
  get '/'
end

Sinatra App:

get '/'
  Logger.write( 'Log message 1' )
  Logger.write( 'Log message 2' )
end

This spec fails because of 'Log message 2'. How to tell RSpec to ignore any other messages, and only test for the expected message?