Calling super from a method in an included module can invoke the wrong superclass (https://github.com/rubinius/rubinius/issues/3783)

rbx_strftime.rb

module Extension
  def strftime(format)    
    super('%Y')
  end
end

class ExtendedTime < Time
  include Extension
end

class ExtendedTime2 < Time
  include Extension
end

class TestClass
  def strftime(format)
    "TestClass: #{format}"
  end
end

class ExtendedTestClass < TestClass
  include Extension
end

puts ExtendedTime.new(2018).strftime('x')
puts ExtendedTime2.new(2018).strftime('x')
3.times { puts ExtendedTestClass.new.strftime('x') }

rbx_strftime_output.txt

2018
2018
TestClass: %Y
TestClass: %Y
                main # Rubinius::Loader at core/loader.rb:852 (+90)
              script # Rubinius::Loader at core/loader.rb:667 (+343)
         load_script # Rubinius::CodeLoader at core/code_loader.rb:280 (+60)
                load # Rubinius::CodeLoader::Source(Rubinius::CodeLoader::Script) at core/code_loader.rb:119 (+81)
          run_script # Rubinius::CodeLoader::Source(Rubinius::CodeLoader::Script) at core/code_loader.rb:132 (+21)
          __script__ # Object at rbx_strftime.rb:27 (+234)
               times # Integer(Fixnum) at core/integer.rb:194 (+40)
   { } in __script__ # Object at rbx_strftime.rb:27 (+35)
            strftime # Extension(ExtendedTestClass) at rbx_strftime.rb:3 (+7)
            strftime # Time(ExtendedTestClass) at core/time.rb:40 (+12)

Time#strftime primitive failed (PrimitiveFailure)

An exception occurred running rbx_strftime.rb