Esprima minification garbles class definitions?

I have this source code

class Field {
  constructor(index, buttonsPerLine) {
    console.log("Constructor called");
  }
}

var f0=new Field(0,3);

When I upload it into the Bangle 2 emulator using the Web IDE, I get "Constructor called" on the console, as expected.

When I upload it with enabled Esprima minification, I get

Uncaught ReferenceError: "Field" is not defined
at line 1 col 61
...Constructor called')}}var f0=new Field(0,3)

When I shrink the source code to simply

class Field {
  constructor(index, buttonsPerLine) {
  }
}

var f0=new Field(0,3);

I see the following error message on uploading the minified code:

Uncaught ReferenceError: "Field" is not defined
at line 1 col 28
class a{constructor(a,b){}}var f0=new Field(0,3)

To me it seems that the Esprima minificator changes the name of the defined class from "Field" to "a" and then cannot find the class "Field" - which is not too surprising…

Is this expected behaviour? Am I doing something wrong? I'm quite new to Javascript programming but to me the code looks totally reasonable.

Any help appreciated!
Best regards,
Dirk

After playing around a bit, I have discovered, that the problem is directly connected to the "Esprima Mangle" option in the Web IDE: If I disable that option, code is transferred correctly.

Could it be that shortening variable names does not handle class definitions correctly?

Could it be that shortening variable names does not handle class definitions correctly?

That sounds entirely likely. I guess we could report this with Esprima but it feels like it's not very well maintained at the moment :(