arrow function doesn't get replaced with ecmascript

Running meteor with --production flag or deploying to Galaxy, one arrow function in fileUpload.js doesn't get replaced with ecmascript and es5-shim installed, and it breaks compatibility in Internet Explorer.
Every other code part works fine, this is the only arrow method that doesn't get replaced.

lib/client/fileUpload.js
starting with line 44
this.collectionName = () => { return this.data.atts.collection; };

Some weird stuff happened: I wanted to poke around see if I can break it with a custom file upload template that I copied from the original.
I tried to store the function in a variable, and I only put the variable above that line, and it worked. Not just this variable was transpiled correctly, but the other one too. When I removed the new code, it was failing again.

  let collectionName = () => {
    return this.collection.collectionName();
  };

  this.collectionName = () => {
    return this.collection.collectionName();
  };

[dr-dimitru]

@balazsbencs-attrecto thank you a lot for reporting about this.
Sorry for delay, fix is published in v2.1.0. Please upgrade to the latest release and let me know how it works for you.