Shebang "# ruby" causes an error on Ubuntu

[ZimbiX]

Test file:

#!/usr/bin/env duct # ruby

puts 'sup'

__END__
@@ Gemfile
source 'https://rubygems.org'
gem 'hex_string'

Error:

2.2.0 in Duct/  
› ./shebang-in-zsh.rb 
/usr/bin/env: duct # ruby: No such file or directory

To be honest, I'm not sure how you'd go about solving this.

It occurs in zsh, bash, and sh