Redefine SASS class.error in ion-item

Hi everyone,

I face a problem with getting into SASS in Ionic 2. I have a login form with user and password:

<form [ngFormModel]="authForm" (submit)="submitLogin($event)">
  <ion-item [class.error]="!username.valid && username.touched">
    <ion-label fixed for="username">Username</ion-label>
    <ion-input type="text" required
    [ngFormControl]="username" name="username"> </ion-input>

  <ion-item [class.error]="!password.valid && password.touched">
    <ion-label fixed for="password">Password</ion-label>
    <ion-input type="text" required
    [ngFormControl]="password" name="password"> </ion-input>

  <button [disabled]="!authForm.valid" type="submit" class="btn btn-default">Submit</button>


Android class.error looks very sexy: a beautiful line under the input field, which helps user understand if his input is valid. However ios doesn’t have it.

What i am looking for?
I am looking for a place, where i can change this. I checked node_modules/ionic-angular/components/item, but i didnt find the definition of the class.error.

Any points?