returning JSON response with multiple models

I am trying to return a JSON response which consists of an array of accounts where each account has one currency(name, rate).

currency.php model:

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class currency extends Model {

    protected $fillable = array('name', 'rate');

    public function group(){
        return $this->belongsTo('account');
    }
}

account.php model:

<?php namespace App;

use Illuminate\Database\Eloquent\Model;

class account extends Model {

    public function currency(){
        return $this->hasOne('currency');
    }

}

and my AccountController:

public function index()
    {
        $accounts = Account::with('currency')->get();

        return $accounts;
    }

No matter what I tried to change i always get this error: Class 'Currency' not found What am I doing wrong?

via Chebli Mohamed