M2M Bug?

class M1(models.Model):
    m2m = models.ManyToManyField(m2)

class M2(models.Model):
    name = models.CharField(unique=True)

---

m = M1.create()
# this passes
m.m2m.get_or_create(name='foo')

an_other_m = M1.create()
# and now this fails:
an_other_m.m2m.get_or_create(name='foo')

#IntegrityError: duplicate key value violates unique constraint "test_m2_name_key"
#DETAIL:  Key (name)=(foo) already exists.