Doesn't work with $DEBUG == true

[yefrem]

Hello guys
I've came across this issue when deployed my app to DigitalOcean VPS pre-configured for Rails app.
I was getting this

too many arguments for format string
/usr/local/rvm/gems/ruby-2.4.0/gems/madmimi-1.1.2/lib/madmimi.rb:358:in `%'
/usr/local/rvm/gems/ruby-2.4.0/gems/madmimi-1.1.2/lib/madmimi.rb:358:in `path'
/usr/local/rvm/gems/ruby-2.4.0/gems/madmimi-1.1.2/lib/madmimi.rb:237:in `send_mail'`

When calling send_mail from controller. Thing is that with $DEBUG == true the line 'smth' % {} raises that error and I've had my unicorn set up to enable debug.
I'm not sure if you think it's worth fixing or not. If you don't maybe noticing this in docs could be a good idea.