diff --git a/src/app/api/workouts/[id]/route.ts b/src/app/api/workouts/[id]/route.ts
index 362f6bef4..f7a7350b9 100644
--- a/src/app/api/workouts/[id]/route.ts
+++ b/src/app/api/workouts/[id]/route.ts
@@ -259,17 +259,22 @@ export const GET = apiHandler(
         null,
       )?.id ?? null;
 
-    const route = row.route
-      ? {
-          geometry: routeGeometry,
-          // `compact=1` drops the (up to 20k-entry) timestamp array; the
-          // SVG needs geometry, not the per-sample timestamps, and the
-          // splits above are already derived from them server-side.
-          sampleTimestamps: compact
-            ? null
-            : (row.route.sampleTimestamps ?? null),
-        }
-      : null;
+    // A route whose track cannot be read (a sealed value that no longer
+    // opens, or an old row stored as a JSON null) is reported as no route at
+    // all: clients decode `route.geometry` as required, so a route object
+    // with a null geometry would fail the whole workout detail for them.
+    const route =
+      row.route && routeGeometry
+        ? {
+            geometry: routeGeometry,
+            // `compact=1` drops the (up to 20k-entry) timestamp array; the
+            // SVG needs geometry, not the per-sample timestamps, and the
+            // splits above are already derived from them server-side.
+            sampleTimestamps: compact
+              ? null
+              : (row.route.sampleTimestamps ?? null),
+          }
+        : null;
 
     // v1.10.0 — route-independent per-workout HR series. Present for
     // both indoor (no route) and outdoor workouts that shipped a
diff --git a/tests/integration/workout-detail-hr-series.test.ts b/tests/integration/workout-detail-hr-series.test.ts
index e578ba906..7f3d904be 100644
--- a/tests/integration/workout-detail-hr-series.test.ts
+++ b/tests/integration/workout-detail-hr-series.test.ts
@@ -23,6 +23,7 @@
  * rather than only in a count.
  */
 import { NextRequest } from "next/server";
+import { Prisma } from "@/generated/prisma/client";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 
 import { cookieJar, headerJar } from "./mock-next-headers";
@@ -277,3 +278,18 @@ describe("GET /api/workouts/{id} — reconstructed heart-rate curve", () => {
     expect(response.status).toBe(404);
   });
 });
+
+describe("GET /api/workouts/{id} — a route whose track cannot be read", () => {
+  it("reports no route at all instead of a route with a null geometry", async () => {
+    const id = await createWorkout();
+    // Neither the sealed column nor the legacy readable one holds a track:
+    // the shape an unreadable or JSON-null row resolves to.
+    await getPrismaClient().workoutRoute.create({
+      data: { workoutId: id, geometry: Prisma.JsonNull },
+    });
+    const body = (await fetchDetail(id)) as unknown as {
+      data: { route: unknown };
+    };
+    expect(body.data.route).toBeNull();
+  });
+});