Accessing the calling class instance method within the module

I want to call a method of the calling class within a module. This worked fine in Version 2v00 of espruino. After updating to 2v01 I get an error with the same code.

This is the calling program:

class a {
  constructor() {
    this.mB = null;
  }
  
  init() {
    this.mB = new (require('http://192.168.88.117:8081/b.js'))(this);
    this.mB.perform();
  }

  say(text) {
    console.log(text);
  }
}

var x = new a();
x.init();

And this is the module:

class b {
  constructor(a) {
    this.a = a;
  }
  
  perform() {
    console.log('class b called');
    this.a.say("I'm in b");
  }
}
exports = b;

The output shows as follows:

Error: Line 8: Unexpected reserved word in http://192.168.88.117:8081/b.js
>
 ____                 _
|  __|___ ___ ___ _ _|_|___ ___
|  __|_ -| . |  _| | | |   | . |
|____|___|  _|_| |___|_|_|_|___|
         |_| espruino.com
 2v00 (c) 2018 G.Williams
Espruino is Open Source. Our work is supported
only by sales of official boards and donations:
http://espruino.com/Donate
Flash map 4MB:512/512, manuf 0xef chip 0x4016
>class b called
I'm in b
Disconnected
>
Found ESP8266_4MB, 2v01
>
Connected to COM4
Error: Line 8: Unexpected reserved word in http://192.168.88.117:8081/b.js
>
 ____                 _
|  __|___ ___ ___ _ _|_|___ ___
|  __|_ -| . |  _| | | |   | . |
|____|___|  _|_| |___|_|_|_|___|
         |_| espruino.com
 2v01 (c) 2018 G.Williams
Espruino is Open Source. Our work is supported
only by sales of official boards and donations:
http://espruino.com/Donate
Flash map 4MB:512/512, manuf 0xef chip 0x4016
>class b called
Uncaught Error: Cannot read property 'say' of undefined
 at line 2 col 11
    this.a.say("I'm in b");
          ^
in function "perform" called from line 10 col 21
    this.mB.perform();
                    ^
in function "init" called from line 19 col 8
x.init();
       ^
> 

It seems that the parameter for the constructor is not passed anymore in 2v01