\mathbb rendering issues

[prairir]

I am not sure if this is an issue with mtex2MML or mathematical

when I run

require 'mathematical'
tex = Mathematical.new(format: :png, ppi: 300.0)
image = tex.render("$\\mathbb{hi}$")
File.open("test.png", "w") { |f| f.write(image[:data])}

or similar code just rendering \mathbb

it returns the text + opf

this is the output of the code above

when separating the characters like \mathbb{h} \mathbb{i} it renders properly

im not sure if im doing something wrong or this is a bug.