diff --git a/scripts/check-migrations.mjs b/scripts/check-migrations.mjs
index 8b62f65366..f8d5862ba0 100644
--- a/scripts/check-migrations.mjs
+++ b/scripts/check-migrations.mjs
@@ -76,4 +76,7 @@ for (let i = 1; i < numbers.length; i += 1) {
 
 const first = String(numbers[0]).padStart(4, "0");
 const last = String(numbers.at(-1)).padStart(4, "0");
-process.stdout.write(`check-migrations: ${files.length} migrations OK — contiguous ${first}..${last} (2 grandfathered duplicates: 0015, 0017), no new duplicates. Next free: ${nextFree()}\n`);
+const grandfatheredNumbers = [...KNOWN_DUPLICATES.keys()]
+  .sort((a, b) => a - b)
+  .map((number) => String(number).padStart(4, "0"));
+process.stdout.write(`check-migrations: ${files.length} migrations OK — contiguous ${first}..${last} (${grandfatheredNumbers.length} grandfathered duplicates: ${grandfatheredNumbers.join(", ")}), no new duplicates. Next free: ${nextFree()}\n`);
diff --git a/test/unit/check-migrations-script.test.ts b/test/unit/check-migrations-script.test.ts
new file mode 100644
index 0000000000..f91e7c7d2d
--- /dev/null
+++ b/test/unit/check-migrations-script.test.ts
@@ -0,0 +1,10 @@
+import { execFileSync } from "node:child_process";
+import { describe, expect, it } from "vitest";
+
+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)");
+  });
+});