diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
index 2a5372b77..3fb4fa2c2 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java
@@ -693,7 +693,7 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     PushChallengeManager pushChallengeManager = new PushChallengeManager(pushNotificationManager,
         pushChallengeDynamoDb);
 
-    ChangeNumberManager changeNumberManager = new ChangeNumberManager(messageSender, accountsManager);
+    ChangeNumberManager changeNumberManager = new ChangeNumberManager(messageSender, accountsManager, Clock.systemUTC());
 
     HttpClient currencyClient = HttpClient.newBuilder().version(HttpClient.Version.HTTP_2).connectTimeout(Duration.ofSeconds(10)).build();
     FixerClient fixerClient = config.getPaymentsServiceConfiguration().externalClients()
diff --git a/service/src/main/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManager.java b/service/src/main/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManager.java
index 2a0700f63..17449a509 100644
--- a/service/src/main/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManager.java
+++ b/service/src/main/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManager.java
@@ -5,6 +5,7 @@
 package org.whispersystems.textsecuregcm.storage;
 
 import com.google.protobuf.ByteString;
+import java.time.Clock;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
@@ -29,12 +30,16 @@ public class ChangeNumberManager {
   private static final Logger logger = LoggerFactory.getLogger(ChangeNumberManager.class);
   private final MessageSender messageSender;
   private final AccountsManager accountsManager;
+  private final Clock clock;
 
   public ChangeNumberManager(
       final MessageSender messageSender,
-      final AccountsManager accountsManager) {
+      final AccountsManager accountsManager,
+      final Clock clock) {
+
     this.messageSender = messageSender;
     this.accountsManager = accountsManager;
+    this.clock = clock;
   }
 
   public Account changeNumber(final Account account, final String number,
@@ -97,7 +102,7 @@ public class ChangeNumberManager {
       final String senderUserAgent) throws MessageTooLargeException, MismatchedDevicesException {
 
     try {
-      final long serverTimestamp = System.currentTimeMillis();
+      final long serverTimestamp = clock.millis();
       final ServiceIdentifier serviceIdentifier = new AciServiceIdentifier(account.getUuid());
 
       final Map<Byte, Envelope> messagesByDeviceId = deviceMessages.stream()
@@ -114,8 +119,8 @@ public class ChangeNumberManager {
               .setEphemeral(false)
               .build()));
 
-      final Map<Byte, Integer> registrationIdsByDeviceId = account.getDevices().stream()
-          .collect(Collectors.toMap(Device::getId, Device::getRegistrationId));
+      final Map<Byte, Integer> registrationIdsByDeviceId = deviceMessages.stream()
+          .collect(Collectors.toMap(IncomingMessage::destinationDeviceId, IncomingMessage::destinationRegistrationId));
 
       messageSender.sendMessages(account,
           serviceIdentifier,
diff --git a/service/src/test/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManagerTest.java b/service/src/test/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManagerTest.java
index 9830a9e35..cfb0bcbce 100644
--- a/service/src/test/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManagerTest.java
+++ b/service/src/test/java/org/whispersystems/textsecuregcm/storage/ChangeNumberManagerTest.java
@@ -9,13 +9,16 @@ import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyByte;
+import static org.mockito.ArgumentMatchers.argThat;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
 
+import com.google.protobuf.ByteString;
 import java.nio.charset.StandardCharsets;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -35,8 +38,10 @@ import org.whispersystems.textsecuregcm.entities.ECSignedPreKey;
 import org.whispersystems.textsecuregcm.entities.IncomingMessage;
 import org.whispersystems.textsecuregcm.entities.KEMSignedPreKey;
 import org.whispersystems.textsecuregcm.entities.MessageProtos;
+import org.whispersystems.textsecuregcm.identity.AciServiceIdentifier;
 import org.whispersystems.textsecuregcm.push.MessageSender;
 import org.whispersystems.textsecuregcm.tests.util.KeysHelper;
+import org.whispersystems.textsecuregcm.util.TestClock;
 
 public class ChangeNumberManagerTest {
   private AccountsManager accountsManager;
@@ -45,11 +50,13 @@ public class ChangeNumberManagerTest {
 
   private Map<Account, UUID> updatedPhoneNumberIdentifiersByAccount;
 
+  private static final TestClock CLOCK = TestClock.pinned(Instant.now());
+
   @BeforeEach
   void setUp() throws Exception {
     accountsManager = mock(AccountsManager.class);
     messageSender = mock(MessageSender.class);
-    changeNumberManager = new ChangeNumberManager(messageSender, accountsManager);
+    changeNumberManager = new ChangeNumberManager(messageSender, accountsManager, CLOCK);
 
     updatedPhoneNumberIdentifiersByAccount = new HashMap<>();
 
@@ -132,45 +139,59 @@ public class ChangeNumberManagerTest {
     when(account.getUuid()).thenReturn(aci);
     when(account.getPhoneNumberIdentifier()).thenReturn(pni);
 
-    final Device d2 = mock(Device.class);
-    final byte deviceId2 = 2;
-    when(d2.getId()).thenReturn(deviceId2);
+    final Device primaryDevice = mock(Device.class);
+    when(primaryDevice.getId()).thenReturn(Device.PRIMARY_ID);
+    when(primaryDevice.getRegistrationId()).thenReturn(7);
 
-    when(account.getDevice(deviceId2)).thenReturn(Optional.of(d2));
-    when(account.getDevices()).thenReturn(List.of(d2));
+    final Device linkedDevice = mock(Device.class);
+    final byte linkedDeviceId = Device.PRIMARY_ID + 1;
+    final int linkedDeviceRegistrationId = 17;
+    when(linkedDevice.getId()).thenReturn(linkedDeviceId);
+    when(linkedDevice.getRegistrationId()).thenReturn(linkedDeviceRegistrationId);
+
+    when(account.getDevice(anyByte())).thenReturn(Optional.empty());
+    when(account.getDevice(Device.PRIMARY_ID)).thenReturn(Optional.of(primaryDevice));
+    when(account.getDevice(linkedDeviceId)).thenReturn(Optional.of(linkedDevice));
+    when(account.getDevices()).thenReturn(List.of(primaryDevice, linkedDevice));
 
     final ECKeyPair pniIdentityKeyPair = Curve.generateKeyPair();
     final IdentityKey pniIdentityKey = new IdentityKey(pniIdentityKeyPair.getPublicKey());
     final Map<Byte, ECSignedPreKey> prekeys = Map.of(Device.PRIMARY_ID,
         KeysHelper.signedECPreKey(1, pniIdentityKeyPair),
-        deviceId2, KeysHelper.signedECPreKey(2, pniIdentityKeyPair));
-    final Map<Byte, Integer> registrationIds = Map.of(Device.PRIMARY_ID, 17, deviceId2, 19);
+        linkedDeviceId, KeysHelper.signedECPreKey(2, pniIdentityKeyPair));
+    final Map<Byte, Integer> registrationIds = Map.of(Device.PRIMARY_ID, 17, linkedDeviceId, 19);
 
     final IncomingMessage msg = mock(IncomingMessage.class);
-    when(msg.destinationDeviceId()).thenReturn(deviceId2);
+    when(msg.type()).thenReturn(1);
+    when(msg.destinationDeviceId()).thenReturn(linkedDeviceId);
+    when(msg.destinationRegistrationId()).thenReturn(linkedDeviceRegistrationId);
     when(msg.content()).thenReturn(new byte[]{1});
 
     changeNumberManager.changeNumber(account, changedE164, pniIdentityKey, prekeys, null, List.of(msg), registrationIds, null);
 
     verify(accountsManager).changeNumber(account, changedE164, pniIdentityKey, prekeys, null, registrationIds);
 
-    @SuppressWarnings("unchecked") final ArgumentCaptor<Map<Byte, MessageProtos.Envelope>> envelopeCaptor =
-        ArgumentCaptor.forClass(Map.class);
+    final MessageProtos.Envelope expectedEnvelope = MessageProtos.Envelope.newBuilder()
+        .setType(MessageProtos.Envelope.Type.forNumber(msg.type()))
+        .setClientTimestamp(CLOCK.millis())
+        .setServerTimestamp(CLOCK.millis())
+        .setDestinationServiceId(new AciServiceIdentifier(aci).toServiceIdentifierString())
+        .setContent(ByteString.copyFrom(msg.content()))
+        .setSourceServiceId(new AciServiceIdentifier(aci).toServiceIdentifierString())
+        .setSourceDevice(Device.PRIMARY_ID)
+        .setUpdatedPni(updatedPhoneNumberIdentifiersByAccount.get(account).toString())
+        .setUrgent(true)
+        .setEphemeral(false)
+        .build();
 
-    verify(messageSender).sendMessages(any(), any(), envelopeCaptor.capture(), any(), any(), any());
-
-    assertEquals(1, envelopeCaptor.getValue().size());
-    assertEquals(Set.of(deviceId2), envelopeCaptor.getValue().keySet());
-
-    final MessageProtos.Envelope envelope = envelopeCaptor.getValue().get(deviceId2);
-
-    assertEquals(aci, UUID.fromString(envelope.getDestinationServiceId()));
-    assertEquals(aci, UUID.fromString(envelope.getSourceServiceId()));
-    assertEquals(Device.PRIMARY_ID, envelope.getSourceDevice());
-    assertEquals(updatedPhoneNumberIdentifiersByAccount.get(account), UUID.fromString(envelope.getUpdatedPni()));
+    verify(messageSender).sendMessages(argThat(a -> a.getUuid().equals(aci)),
+        eq(new AciServiceIdentifier(aci)),
+        eq(Map.of(linkedDeviceId, expectedEnvelope)),
+        eq(Map.of(linkedDeviceId, linkedDeviceRegistrationId)),
+        eq(Optional.of(Device.PRIMARY_ID)),
+        any());
   }
 
-
   @Test
   void changeNumberSetPrimaryDevicePrekeyPqAndSendMessages() throws Exception {
     final String originalE164 = "+18005551234";