diff --git a/docs/superpowers/plans/2026-09-15-m1-data-collection-foundation.md b/docs/superpowers/plans/2026-09-15-m1-data-collection-foundation.md
index 422315c..5faca5a 100644
--- a/docs/superpowers/plans/2026-09-15-m1-data-collection-foundation.md
+++ b/docs/superpowers/plans/2026-09-15-m1-data-collection-foundation.md
@@ -333,7 +333,8 @@ def test_visitor_first_touch_fields():
 def test_event_unique_site_event_id():
     site = Site.objects.create(name="s", domains=["a.com"])
     v = Visitor.objects.create(site=site, visitor_id="vid1")
-    s = VisitSession.objects.create(site=site, visitor=v, session_id="sid1")
+    s = VisitSession.objects.create(site=site, visitor=v, session_id="sid1",
+        started_at="2026-09-15T10:00:00Z", ended_at="2026-09-15T10:01:00Z")
     Event.objects.create(site=site, visitor=v, session=s, event_id="e1",
         event_name="page_view", occurred_at="2026-09-15T10:00:00Z", path="/")
     with pytest.raises(Exception):