Duplicate results in Q query involving many to one relation to a model

Duplicate results in Q query involving many to one relation to a model

I have a Car model and a Passenger model with a ForeignKey to a Car
object. Both Car and Passenger models have a name field.
I want to get all the cars that contain 'banana' in either the car or any
passenger name, so I tried:
from django.db.models import Q
...
name = 'banana'
cars = Car.objects.filter(Q(name__icontains=name) |
Q(passenger__name__icontains=name))
Curiously, when I have a Car named 'banana' and three passengers in it
called anything (matching or not 'banana'), it returns three times the
matching Car.
The questions are:
Why?
How to return only once the car? I think that .distinct() would work, but
maybe there is a better way.
I am using Django 1.5.