diff --git a/example/src/test_tanker.ts b/example/src/test_tanker.ts
index 83b4f19..37661b2 100644
--- a/example/src/test_tanker.ts
+++ b/example/src/test_tanker.ts
@@ -11,7 +11,11 @@ import {
   getVerificationCode,
   toggleSessionCertificates,
 } from './admin';
-import { InvalidArgument, InvalidVerification } from '@tanker/errors';
+import {
+  InvalidArgument,
+  InvalidVerification,
+  IdentityAlreadyAttached,
+} from '@tanker/errors';
 import { createTanker, clearTankerDataDirs } from './tests';
 import base64 from 'react-native-base64';
 
@@ -212,6 +216,33 @@ export const tankerTests = () => {
       await tanker.verifyProvisionalIdentity({ email, verificationCode });
     });
 
+    it('throws when attaching an already attached provisional identity', async () => {
+      await tanker.start(identity);
+      await tanker.registerIdentity({
+        passphrase: 'ice cold water',
+      });
+      const email = 'bob@burger.io';
+      const provIdentity = await createProvisionalIdentity(email);
+      const result = await tanker.attachProvisionalIdentity(provIdentity);
+      expect(result.verificationMethod).deep.eq({ type: 'email', email });
+
+      const verificationCode = await getVerificationCode(email);
+      await tanker.verifyProvisionalIdentity({ email, verificationCode });
+
+      const other = await createTanker();
+      await other.start(await createIdentity());
+      await other.registerIdentity({ passphrase: 'otherpass' });
+      other.attachProvisionalIdentity(provIdentity);
+      expect(result.status).eq(Tanker.statuses.IDENTITY_VERIFICATION_NEEDED);
+      const verificationCode2 = await getVerificationCode(email);
+      await expect(
+        other.verifyProvisionalIdentity({
+          email,
+          verificationCode: verificationCode2,
+        })
+      ).to.be.rejectedWith(IdentityAlreadyAttached);
+    });
+
     it('can skip provisional identity verification', async () => {
       const email = 'bob@bargor.io';
       const provIdentity = await createProvisionalIdentity(email);
diff --git a/ios/Utils+Private.m b/ios/Utils+Private.m
index cd80ca4..23c3d4c 100644
--- a/ios/Utils+Private.m
+++ b/ios/Utils+Private.m
@@ -136,6 +136,8 @@ void rejectWithError(RCTPromiseRejectBlock _Nonnull reject, NSError* _Nonnull er
       return @"DEVICE_REVOKED";
     case TKRErrorUpgradeRequired:
       return @"UPGRADE_REQUIRED";
+    case TKRErrorIdentityAlreadyAttached:
+      return @"IDENTITY_ALREADY_ATTACHED";
     default:
       return @"UNKNOWN_ERROR";
   }
diff --git a/src/errors.ts b/src/errors.ts
index 231fdcd..bc89285 100644
--- a/src/errors.ts
+++ b/src/errors.ts
@@ -12,6 +12,7 @@ import {
   DeviceRevoked,
   Conflict,
   UpgradeRequired,
+  IdentityAlreadyAttached,
   TankerError,
 } from '@tanker/errors';
 
@@ -33,6 +34,7 @@ export const errors = {
   TankerError,
   TooManyAttempts,
   UpgradeRequired,
+  IdentityAlreadyAttached,
 };
 
 function translateException(e: any): never {
@@ -67,6 +69,8 @@ function translateException(e: any): never {
       throw new Conflict(e.message);
     case 'UPGRADE_REQUIRED':
       throw new UpgradeRequired(e.message);
+    case 'IDENTITY_ALREADY_ATTACHED':
+      throw new IdentityAlreadyAttached(e.message);
     default:
       // This could be something else than a TankerException, do not wrap or convert to avoid losing information
       throw e;