diff --git a/scripts/check-migrations.mjs b/scripts/check-migrations.mjs
index 8d5ca2a30d..63aabd2a81 100644
--- a/scripts/check-migrations.mjs
+++ b/scripts/check-migrations.mjs
@@ -17,6 +17,8 @@
 //   • 0074 — both 0074_ai_review_cache (#1462) and 0074_orb_self_enrollment_disabled (#1465, a bare ADD COLUMN)
 //     merged + deployed before the collision surfaced; the column already exists in prod, so a rename would
 //     re-run the ALTER and fail. Grandfathered for the same reason as 0015/0017.
+//   • 0090 — both 0090_contributor_cap_label (#2479) and 0090_pull_request_detail_sync_head_sha (#2527, a bare
+//     ADD COLUMN) merged + deployed before the collision surfaced. Grandfathered for the same reason as 0074.
 import { readdirSync, readFileSync } from "node:fs";
 
 const DIR = process.env.CHECK_MIGRATIONS_DIR || "migrations";
@@ -25,6 +27,7 @@ const KNOWN_DUPLICATES = new Map([
   [15, new Set(["0015_github_agent_command_feedback.sql", "0015_product_usage_events.sql"])],
   [17, new Set(["0017_agent_recommendation_outcomes.sql", "0017_product_usage_role_retention_rollups.sql"])],
   [74, new Set(["0074_ai_review_cache.sql", "0074_orb_self_enrollment_disabled.sql"])],
+  [90, new Set(["0090_contributor_cap_label.sql", "0090_pull_request_detail_sync_head_sha.sql"])],
 ]);
 
 const fail = (message) => {
diff --git a/test/unit/check-migrations-script.test.ts b/test/unit/check-migrations-script.test.ts
index 1320c32f88..65bbb20066 100644
--- a/test/unit/check-migrations-script.test.ts
+++ b/test/unit/check-migrations-script.test.ts
@@ -31,7 +31,7 @@ describe("check-migrations script", () => {
   it("reports every grandfathered duplicate migration number in the success summary", () => {
     const output = execFileSync(process.execPath, ["scripts/check-migrations.mjs"], { encoding: "utf8" });
 
-    expect(output).toContain("(3 grandfathered duplicates: 0015, 0017, 0074)");
+    expect(output).toContain("(4 grandfathered duplicates: 0015, 0017, 0074, 0090)");
   });
 
   it("rejects a migration that creates a temporary object (the D1 remote authorizer blocks it)", () => {