diff --git a/plugins/auth-backend/src/identity/FirestoreKeyStore.test.ts b/plugins/auth-backend/src/identity/FirestoreKeyStore.test.ts
index b04cf8a6b3..8e30dcc6f8 100644
--- a/plugins/auth-backend/src/identity/FirestoreKeyStore.test.ts
+++ b/plugins/auth-backend/src/identity/FirestoreKeyStore.test.ts
@@ -24,7 +24,9 @@ import {
 } from './FirestoreKeyStore';
 import { AnyJWK } from './types';
 
-const data = jest.fn().mockReturnValue('data');
+const data = jest
+  .fn()
+  .mockReturnValue({ key: { kid: 'something' }, kid: 'something' });
 const toDate = jest.fn().mockReturnValue('date');
 const get = jest.fn().mockReturnValue({
   docs: [{ data, createTime: { toDate } }],
@@ -145,7 +147,7 @@ describe('FirestoreKeyStore', () => {
     expect(firestoreMock.doc).toHaveBeenCalledWith(key.kid);
     expect(firestoreMock.set).toHaveBeenCalledWith({
       kid: key.kid,
-      key: JSON.stringify(key),
+      key,
     });
   });
 
@@ -180,7 +182,26 @@ describe('FirestoreKeyStore', () => {
     expect(data).toHaveBeenCalledTimes(1);
     expect(toDate).toHaveBeenCalledTimes(1);
     expect(items).toMatchObject({
-      items: [{ key: 'data', createdAt: 'date' }],
+      items: [{ key: { kid: 'something' }, createdAt: 'date' }],
+    });
+  });
+
+  it('supports older string versions of the keys', async () => {
+    data.mockReturnValue({
+      key: JSON.stringify({ kid: 'something' }),
+      kid: 'something',
+    });
+
+    const keyStore = await FirestoreKeyStore.create(firestoreSettings);
+    const items = await keyStore.listKeys();
+
+    expect(setTimeout).toHaveBeenCalledTimes(1);
+    expect(firestoreMock.collection).toHaveBeenCalledWith(path);
+    expect(firestoreMock.get).toHaveBeenCalledTimes(1);
+    expect(data).toHaveBeenCalledTimes(1);
+    expect(toDate).toHaveBeenCalledTimes(1);
+    expect(items).toMatchObject({
+      items: [{ key: { kid: 'something' }, createdAt: 'date' }],
     });
   });
 });
diff --git a/plugins/auth-backend/src/identity/FirestoreKeyStore.ts b/plugins/auth-backend/src/identity/FirestoreKeyStore.ts
index b5f4f5dcfb..3b998a4fe9 100644
--- a/plugins/auth-backend/src/identity/FirestoreKeyStore.ts
+++ b/plugins/auth-backend/src/identity/FirestoreKeyStore.ts
@@ -75,13 +75,10 @@ export class FirestoreKeyStore implements KeyStore {
 
   async addKey(key: AnyJWK): Promise<void> {
     await this.withTimeout<WriteResult>(
-      this.database
-        .collection(this.path)
-        .doc(key.kid)
-        .set({
-          kid: key.kid,
-          key: JSON.stringify(key),
-        }),
+      this.database.collection(this.path).doc(key.kid).set({
+        kid: key.kid,
+        key: key,
+      }),
     );
   }
 
@@ -91,10 +88,14 @@ export class FirestoreKeyStore implements KeyStore {
     );
 
     return {
-      items: keys.docs.map(key => ({
-        key: key.data() as AnyJWK,
-        createdAt: key.createTime.toDate(),
-      })),
+      items: keys.docs.map(doc => {
+        const { key } = doc.data();
+
+        return {
+          createdAt: doc.createTime.toDate(),
+          key: typeof key === 'string' ? JSON.parse(key) : key,
+        };
+      }),
     };
   }