Support for ie11 in UMD module ?

[Morphexe]

This issue is a:

• Question / support request

If I am using export as UMD module, how can I enable support for ie11 ?
It currently exports with some invalid syntax (class Something...), it seems this doesn't respect the

browsers : { 
    production: '>0.5%, IE 11'
  },

in nwb.config.js

Did I misconfigured something