Cannot bind Livewire to Model

We're using the following code to bind to a $state array:

```
<x-tel-input
wire:model.defer="state.{{$key}}"
wire:key="{{$key}}"
class="form-input"
/>
```
However, the phone number is never saved and is empty in the array. We've tried to use defer, lazy etc.

I'm not sure if would make a difference, but we have two fields, a phone and a phone confirmation.