Prod Build Error - "Calling function 'ɵmakeDecorator'"

I get this error when trying to build prod, ionic build --prod

Error: Error encountered resolving symbol values statically. Calling function ‘ɵmakeDecorator’, function calls are not supported.

Here’s my ionic info -

    ionic (Ionic CLI) : 3.13.1

global packages:

    cordova (Cordova CLI) : 7.0.1 

local packages:

    @ionic/app-scripts : 2.1.3
    Cordova Platforms  : browser 4.1.0
    Ionic Framework    : ionic-angular 3.6.0


    Node  : v8.4.0
    npm   : 5.5.1 
    OS    : macOS Sierra
    Xcode : Xcode 9.2 Build version 9C40b 


    backend : pro

I’m not sure this makes a difference, but I am lazy loading all my pages in this app. Could this be the problem?