diff --git a/ghost/tiers/lib/Tier.js b/ghost/tiers/lib/Tier.js
index 2040c86841..8a40c71655 100644
--- a/ghost/tiers/lib/Tier.js
+++ b/ghost/tiers/lib/Tier.js
@@ -186,7 +186,7 @@ module.exports = class Tier {
 
     toJSON() {
         return {
-            id: this.#id,
+            id: this.#id.toHexString(),
             slug: this.#slug,
             name: this.#name,
             description: this.#description,
diff --git a/ghost/tiers/test/Tier.test.js b/ghost/tiers/test/Tier.test.js
index 546a9050d9..51ed7286b9 100644
--- a/ghost/tiers/test/Tier.test.js
+++ b/ghost/tiers/test/Tier.test.js
@@ -99,7 +99,6 @@ describe('Tier', function () {
             const tier = await Tier.create(validInput);
 
             const expectedProps = [
-                'id',
                 'slug',
                 'name',
                 'description',
@@ -119,6 +118,7 @@ describe('Tier', function () {
             for (const prop of expectedProps) {
                 assert(tier[prop] === tier.toJSON()[prop]);
             }
+            assert(tier.id.toHexString() === tier.toJSON().id);
         });
 
         it('Errors when attempting to set invalid properties', async function () {