Conflicting Treatment Slugs

[Sepero]

In the middleware function process_template_response, the following line is used:
request.session[EXPERIMENT_PREFIX+treatment.experiment.slug] = treatment.slug

This sets the treatment.slug in the session (not the treatment.id). What if there are +2 treatments with the same treatment.slug?

The treatment.slug is later retrieved in middleware function process_view, to reverse find the Treatment it belongs to.
treatment_slug = request.session[EXPERIMENT_PREFIX+goal.experiment.slug]
treatment = Treatment.objects.get(slug=treatment_slug)

If +2 Treatments use the same treatment.slug, then the developer cannot be sure which will be retrieved (or perhaps an error will occur?)