Error after upgrading to RC 1

Ionic Framework ionic-v3
1

Hello, After upgrading to RC 1 I get a black screen and an error in the console
Uncaught SyntaxError: Unexpected token < in JSON at position 0
After checking a bit it looks like the error is coming from this:

/* unused harmony export Config */
var Config = JSON.parse('<%= ENV_CONFIG %>');

in the main.js file generated by ionic.

Any idea ?