redex: problem with firebase

I’ve this runtimeException:

10-06 13:58:42.867 E/AndroidRuntime(25200): java.lang.RuntimeException: Unable to get provider com.google.firebase.provider.FirebaseInitProvider: java.lang.IllegalStateException: com.google.firebase.auth.FirebaseAuth#getInstance has been removed by Proguard. Add keep rule to prevent it. 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread.installProvider(ActivityThread.java:5216) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread.installContentProviders(ActivityThread.java:4808) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread.handleBindApplication(ActivityThread.java:4748) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread.-wrap1(ActivityThread.java) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1421) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.os.Handler.dispatchMessage(Handler.java:102) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.os.Looper.loop(Looper.java:148) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread.main(ActivityThread.java:5480) 10-06 13:58:42.867 E/AndroidRuntime(25200): at java.lang.reflect.Method.invoke(Native Method) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 10-06 13:58:42.867 E/AndroidRuntime(25200): Caused by: java.lang.IllegalStateException: com.google.firebase.auth.FirebaseAuth#getInstance has been removed by Proguard. Add keep rule to prevent it. 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.google.firebase.FirebaseApp.a(Unknown Source) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.google.firebase.FirebaseApp.a(Unknown Source) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.google.firebase.FirebaseApp.a(Unknown Source) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.google.firebase.FirebaseApp.a(Unknown Source) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.google.firebase.provider.FirebaseInitProvider.onCreate(Unknown Source) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.content.ContentProvider.attachInfo(ContentProvider.java:1748) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.content.ContentProvider.attachInfo(ContentProvider.java:1723) 10-06 13:58:42.867 E/AndroidRuntime(25200): at com.google.firebase.provider.FirebaseInitProvider.attachInfo(Unknown Source) 10-06 13:58:42.867 E/AndroidRuntime(25200): at android.app.ActivityThread.installProvider(ActivityThread.java:5213) 10-06 13:58:42.867 E/AndroidRuntime(25200): ... 10 more

without redex, the release apk with proguard active, is working.