diff --git a/packages/db/migrations/0013_podcasts_cadence.sql b/packages/db/migrations/0013_podcasts_cadence.sql
new file mode 100644
index 0000000..087e5e5
--- /dev/null
+++ b/packages/db/migrations/0013_podcasts_cadence.sql
@@ -0,0 +1,29 @@
+-- The podcasts sources actually poll every fifteen minutes.
+--
+-- #34 set `cadenceMinutes: 15` on the adapter, which decides what a source is
+-- created with and nothing else. `insertSource` is idempotent on the slug and
+-- its conflict clause updates `name`, `description` and `updated_at` -- not
+-- `config`, and not `cadence_minutes`. That is deliberate: cadence is on the
+-- list of things an operator may edit from the sources page, so re-asserting
+-- the adapter's number on every boot would silently undo a human's decision the
+-- next time the web app restarted.
+--
+-- The cost of that is this file. The two podcast sources were created while the
+-- adapter still said 60, so they kept 60, and the change in #34 reached exactly
+-- nothing that was already running. Nothing failed and no run errored; the
+-- catalogue walk simply proceeded at a quarter of the intended rate, which is
+-- the kind of wrong that is only visible if you go and look.
+--
+-- So the two rows are moved by hand, once. Scoped by slug rather than by
+-- adapter so a source somebody added themselves against the same adapter keeps
+-- whatever cadence they chose for it, and conditional on the current value
+-- still being 60 so that re-running this never overwrites a later decision.
+--
+-- A fresh deployment reaches the same place without this: seeding creates both
+-- sources from the adapter, which now says 15.
+
+update sources
+   set cadence_minutes = 15,
+       updated_at = now()
+ where slug in ('podcasts-commercial', 'podcasts-self-hosted')
+   and cadence_minutes = 60;
diff --git a/test/schema.test.js b/test/schema.test.js
index 65ebd89..ec67128 100644
--- a/test/schema.test.js
+++ b/test/schema.test.js
@@ -933,3 +933,56 @@ describe('the weather collection migration', () => {
     expect(moved).toEqual({ sources: 1, items: 1, feeds: 1, left_behind: 0 });
   });
 });
+
+describe('the podcasts cadence migration', () => {
+  test('moves the two seeded sources to fifteen minutes and nothing else', async () => {
+    // The gap 0013 closes: `insertSource` is idempotent on the slug but its
+    // conflict clause never touches cadence_minutes, so raising the adapter's
+    // cadence reached nothing that already existed.
+    const c = await one(
+      `insert into collections (slug, name) values ('podcasts', 'Podcasts')
+       on conflict (slug) do update set name = excluded.name returning id`,
+    );
+    for (const [slug, cadence] of [
+      ['podcasts-commercial', 60],
+      ['podcasts-self-hosted', 60],
+      // Somebody's own source against the same adapter, and one an operator has
+      // already tuned. Neither may be touched.
+      ['podcasts-mine', 60],
+      ['podcasts-self-hosted-tuned', 5],
+    ]) {
+      await db.query(
+        `insert into sources (collection_id, adapter, slug, name, cadence_minutes)
+         values ($1, 'podcasts', $2, $2, $3)`,
+        [c.id, slug, cadence],
+      );
+    }
+    // Exactly the statement migration 0013 runs.
+    const stmt = `update sources set cadence_minutes = 15, updated_at = now()
+                   where slug in ('podcasts-commercial', 'podcasts-self-hosted')
+                     and cadence_minutes = 60`;
+    await db.query(stmt);
+
+    const after = await one(
+      `select
+         (select cadence_minutes from sources where slug = 'podcasts-commercial') as commercial,
+         (select cadence_minutes from sources where slug = 'podcasts-self-hosted') as self_hosted,
+         (select cadence_minutes from sources where slug = 'podcasts-mine') as mine,
+         (select cadence_minutes from sources where slug = 'podcasts-self-hosted-tuned') as tuned`,
+    );
+    expect(after).toEqual({ commercial: 15, self_hosted: 15, mine: 60, tuned: 5 });
+
+    // Re-running must not walk a later decision back to 15.
+    await db.query(`update sources set cadence_minutes = 60 where slug = 'podcasts-commercial'`);
+    await db.query(`update sources set cadence_minutes = 30 where slug = 'podcasts-self-hosted'`);
+    await db.query(stmt);
+    const again = await one(
+      `select
+         (select cadence_minutes from sources where slug = 'podcasts-commercial') as commercial,
+         (select cadence_minutes from sources where slug = 'podcasts-self-hosted') as self_hosted`,
+    );
+    // The first was genuinely back at 60, so it moves again; the second was
+    // deliberately set to 30 and is left alone.
+    expect(again).toEqual({ commercial: 15, self_hosted: 30 });
+  });
+});