Build error when using --prod

Hello

All of a sudden I get build errors when using ionic cordova build ios --prod. Any advice on whats going on? Building without --prod works fine.

[14:04:13] build prod started …
[14:04:13] clean started …
[14:04:13] clean finished in 2 ms
[14:04:13] copy started …
[14:04:13] ngc started …
[WARN] Error occurred during command execution from a CLI plugin (@ionic/cli-plugin-cordova). Your plugins may be out of date.
Error: Error encountered resolving symbol values statically. Calling function ‘ɵmakeDecorator’, function calls are not supported. Consider replacing the function or lambda with a reference to an exported function, resolving symbol Injectable in /Users/jakob/Code/hypnose-voksen/node_modules/ionic-audio/node_modules/@angular/core/core.d.ts, resolving symbol ɵf in /Users/jakob/Code/hypnose-voksen/node_modules/ionic-audio/node_modules/@angular/core/core.d.ts, resolving symbol ɵf in /Users/jakob/Code/hypnose-voksen/node_modules/ionic-audio/node_modules/@angular/core/core.d.ts

ionic info

global packages:

@ionic/cli-utils : 1.4.0
Cordova CLI      : 7.0.1 
Ionic CLI        : 3.4.0

local packages:

@ionic/app-scripts              : 1.3.7
@ionic/cli-plugin-cordova       : 1.4.0
@ionic/cli-plugin-ionic-angular : 1.3.1
Cordova Platforms               : android 6.2.2 ios 4.4.0
Ionic Framework                 : ionic-angular 3.4.2

System:

Node       : v6.11.0
OS         : macOS Sierra
Xcode      : Xcode 8.3.3 Build version 8E3004b 
ios-deploy : 1.9.1 
ios-sim    : 6.0.0 
npm        : 3.10.10

Please post your app.module.ts.