Laravel required if validation issue

Laravel required if validation issue

Blade:

           
        <div class="form-group row">
            
            <div class="col-md-9">
                
            </div>
        </div>
        <div class="form-group row">
            <label class="col-md-3 col-form-label font-weight-bold">Mandrill</label>
        </div>
        <div class="form-group row">
            
            <div class="col-md-9">
                
            </div>
        </div>
        <div class="form-group row">
            <div class="col-md-9 ml-md-auto">
                
                 <a class="btn btn-danger" href=""><i class="far fa-times-circle"></i> Cancel</a>
            </div>
        </div>
    

Form Request:

    return [
        'driver' => 'required',
        'mailgun.*.domain' => 'required_if:driver,mailgun'
    ];

Validation always fails. Please suggest me if i miss anything.

via Chebli Mohamed