Relationship withTrashed() returns null

I'm using soft delete for my Student::class model.

I want to retrieve the soft deleted model in my booking log like this:

Booking::class

// Normal relationship works when student is not softdeleted
public function student()
{
    return $this->belongsTo(Student::class);
}

// This doesn't work, returns null
public function studentRecord()
{
    return $this->belongsTo(Student::class)->withTrashed();
 }

// This temp patch method works but i can not use with Eager loading
public function studentRecordTemp()
{
    return Student::withTrashed()->find($this->student_id);
}

I really can not understand why the second one is returning null. The student_id is defined if i dump the Booking model.

Thanks