diff --git a/lobby/tests.py b/lobby/tests.py
index bb6f6d5..081fa1c 100644
--- a/lobby/tests.py
+++ b/lobby/tests.py
@@ -788,6 +788,88 @@ class CanonicalRoundFlowTests(TestCase):
         self.assertEqual([entry["nickname"] for entry in payload["scoreboard"]], ["Luna", "Nora", "Mads"])
         self.assertEqual(payload["reveal"]["correct_answer"], "Shakespeare")
 
+    @patch("lobby.views.sync_broadcast_phase_event")
+    @patch("lobby.views._resolve_scores")
+    @patch("lobby.views.GameSession.objects.get")
+    def test_submit_guess_skips_rescore_when_locked_session_is_already_revealing(
+        self,
+        mock_session_get,
+        mock_resolve_scores,
+        mock_sync_broadcast,
+    ):
+        round_config = RoundConfig.objects.create(
+            session=self.session,
+            number=1,
+            category=self.category,
+            points_correct=5,
+            points_bluff=2,
+        )
+        round_question = RoundQuestion.objects.create(
+            session=self.session,
+            round_number=1,
+            question=self.question,
+            correct_answer="Shakespeare",
+        )
+        LieAnswer.objects.create(round_question=round_question, player=self.players[0], text="Marlowe")
+        Guess.objects.create(
+            round_question=round_question,
+            player=self.players[0],
+            selected_text="Shakespeare",
+            is_correct=True,
+        )
+        Guess.objects.create(
+            round_question=round_question,
+            player=self.players[1],
+            selected_text="Marlowe",
+            is_correct=False,
+            fooled_player=self.players[0],
+        )
+        self.players[0].score = round_config.points_correct + round_config.points_bluff
+        self.players[0].save(update_fields=["score"])
+        ScoreEvent.objects.create(
+            session=self.session,
+            player=self.players[0],
+            delta=round_config.points_correct,
+            reason="guess_correct",
+            meta={"round_question_id": round_question.id, "guess_id": 1},
+        )
+        ScoreEvent.objects.create(
+            session=self.session,
+            player=self.players[0],
+            delta=round_config.points_bluff,
+            reason="bluff_success",
+            meta={"round_question_id": round_question.id, "fooled_count": 1},
+        )
+        self.session.status = GameSession.Status.REVEAL
+        self.session.save(update_fields=["status"])
+
+        stale_session = GameSession(
+            pk=self.session.pk,
+            host=self.host,
+            code=self.session.code,
+            status=GameSession.Status.GUESS,
+            current_round=self.session.current_round,
+        )
+        mock_session_get.return_value = stale_session
+
+        response = self.client.post(
+            reverse("lobby:submit_guess", kwargs={"code": self.session.code, "round_question_id": round_question.id}),
+            data={
+                "player_id": self.players[2].id,
+                "session_token": self.players[2].session_token,
+                "selected_text": "Shakespeare",
+            },
+            content_type="application/json",
+        )
+
+        self.assertEqual(response.status_code, 201)
+        self.assertEqual(response.json()["session"]["status"], GameSession.Status.REVEAL)
+        self.assertTrue(response.json()["phase_transition"]["auto_advanced"])
+        self.assertIsNotNone(response.json()["reveal"])
+        mock_resolve_scores.assert_not_called()
+        mock_sync_broadcast.assert_not_called()
+        self.assertEqual(ScoreEvent.objects.filter(session=self.session, meta__round_question_id=round_question.id).count(), 2)
+
 
 class ScoreCalculationTests(TestCase):
     def setUp(self):
diff --git a/lobby/views.py b/lobby/views.py
index 7ab41ee..804404d 100644
--- a/lobby/views.py
+++ b/lobby/views.py
@@ -954,35 +954,59 @@ def submit_guess(request: HttpRequest, code: str, round_question_id: int) -> Jso
     leaderboard = None
 
     if players_count > 0 and guess_count >= players_count:
-        already_calculated = ScoreEvent.objects.filter(
-            session=session,
-            meta__round_question_id=round_question.id,
-        ).exists()
-        if not already_calculated:
-            score_events, leaderboard = _resolve_scores(session, round_question, round_config)
-        else:
-            score_events = list(
-                ScoreEvent.objects.filter(session=session, meta__round_question_id=round_question.id).select_related("player")
-            )
-            leaderboard = _build_leaderboard(session)
+        score_events = []
+        should_broadcast_scores = False
+
+        with transaction.atomic():
+            locked_session = GameSession.objects.select_for_update().get(pk=session.pk)
+
+            if locked_session.status == GameSession.Status.GUESS:
+                already_calculated = ScoreEvent.objects.filter(
+                    session=locked_session,
+                    meta__round_question_id=round_question.id,
+                ).exists()
+                if not already_calculated:
+                    score_events, leaderboard = _resolve_scores(locked_session, round_question, round_config)
+                    should_broadcast_scores = True
+                else:
+                    score_events = list(
+                        ScoreEvent.objects.filter(
+                            session=locked_session,
+                            meta__round_question_id=round_question.id,
+                        ).select_related("player")
+                    )
+                    leaderboard = _build_leaderboard(locked_session)
+
+                locked_session.status = GameSession.Status.REVEAL
+                locked_session.save(update_fields=["status"])
+
+            elif locked_session.status == GameSession.Status.REVEAL:
+                score_events = list(
+                    ScoreEvent.objects.filter(
+                        session=locked_session,
+                        meta__round_question_id=round_question.id,
+                    ).select_related("player")
+                )
+                leaderboard = _build_leaderboard(locked_session)
+
+            session_status = locked_session.status
 
-        session.status = GameSession.Status.REVEAL
-        session.save(update_fields=["status"])
-        session_status = session.status
         reveal_payload = _build_reveal_payload(round_question)
-        score_deltas = [
-            {"player_id": ev.player_id, "delta": ev.delta, "reason": ev.reason}
-            for ev in score_events
-        ]
-        sync_broadcast_phase_event(
-            session.code,
-            "phase.scores_calculated",
-            {
-                "round_question_id": round_question.id,
-                "score_deltas": score_deltas,
-                "leaderboard": list(leaderboard),
-            },
-        )
+
+        if should_broadcast_scores:
+            score_deltas = [
+                {"player_id": ev.player_id, "delta": ev.delta, "reason": ev.reason}
+                for ev in score_events
+            ]
+            sync_broadcast_phase_event(
+                session.code,
+                "phase.scores_calculated",
+                {
+                    "round_question_id": round_question.id,
+                    "score_deltas": score_deltas,
+                    "leaderboard": list(leaderboard),
+                },
+            )
 
     return JsonResponse(
         {