diff --git a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/changenumber/ChangeNumberRepository.kt b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/changenumber/ChangeNumberRepository.kt
index 3b65b0e7a9..0af4d043e4 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/changenumber/ChangeNumberRepository.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/components/settings/app/changenumber/ChangeNumberRepository.kt
@@ -7,7 +7,9 @@ import io.reactivex.rxjava3.schedulers.Schedulers
 import org.signal.core.util.logging.Log
 import org.signal.libsignal.protocol.IdentityKeyPair
 import org.signal.libsignal.protocol.SignalProtocolAddress
+import org.signal.libsignal.protocol.state.KyberPreKeyRecord
 import org.signal.libsignal.protocol.state.SignalProtocolStore
+import org.signal.libsignal.protocol.state.SignedPreKeyRecord
 import org.signal.libsignal.protocol.util.KeyHelper
 import org.signal.libsignal.protocol.util.Medium
 import org.thoughtcrime.securesms.crypto.IdentityKeyUtil
@@ -38,6 +40,7 @@ import org.whispersystems.signalservice.api.push.ServiceIdType
 import org.whispersystems.signalservice.api.push.SignalServiceAddress
 import org.whispersystems.signalservice.api.push.SignedPreKeyEntity
 import org.whispersystems.signalservice.internal.ServiceResponse
+import org.whispersystems.signalservice.internal.push.KyberPreKeyEntity
 import org.whispersystems.signalservice.internal.push.OutgoingPushMessage
 import org.whispersystems.signalservice.internal.push.RegistrationSessionMetadataResponse
 import org.whispersystems.signalservice.internal.push.SignalServiceProtos.SyncMessage
@@ -320,6 +323,7 @@ class ChangeNumberRepository(
     val pniIdentity: IdentityKeyPair = if (pniUpdateMode) SignalStore.account().pniIdentityKey else IdentityKeyUtil.generateIdentityKeyPair()
     val deviceMessages = mutableListOf<OutgoingPushMessage>()
     val devicePniSignedPreKeys = mutableMapOf<Int, SignedPreKeyEntity>()
+    val devicePniLastResortKyberPreKeys = mutableMapOf<Int, KyberPreKeyEntity>()
     val pniRegistrationIds = mutableMapOf<Int, Int>()
     val primaryDeviceId: Int = SignalServiceAddress.DEFAULT_DEVICE_ID
 
@@ -329,7 +333,7 @@ class ChangeNumberRepository(
       .filter { it == primaryDeviceId || aciProtocolStore.containsSession(SignalProtocolAddress(selfIdentifier, it)) }
       .forEach { deviceId ->
         // Signed Prekeys
-        val signedPreKeyRecord = if (deviceId == primaryDeviceId) {
+        val signedPreKeyRecord: SignedPreKeyRecord = if (deviceId == primaryDeviceId) {
           if (pniUpdateMode) {
             ApplicationDependencies.getProtocolStore().pni().loadSignedPreKey(SignalStore.account().pniPreKeys.activeSignedPreKeyId)
           } else {
@@ -340,6 +344,18 @@ class ChangeNumberRepository(
         }
         devicePniSignedPreKeys[deviceId] = SignedPreKeyEntity(signedPreKeyRecord.id, signedPreKeyRecord.keyPair.publicKey, signedPreKeyRecord.signature)
 
+        // Last-resort kyber prekeys
+        val lastResortKyberPreKeyRecord: KyberPreKeyRecord = if (deviceId == primaryDeviceId) {
+          if (pniUpdateMode) {
+            ApplicationDependencies.getProtocolStore().pni().loadKyberPreKey(SignalStore.account().pniPreKeys.lastResortKyberPreKeyId)
+          } else {
+            PreKeyUtil.generateAndStoreLastResortKyberPreKey(ApplicationDependencies.getProtocolStore().pni(), SignalStore.account().pniPreKeys, pniIdentity.privateKey)
+          }
+        } else {
+          PreKeyUtil.generateKyberPreKey(SecureRandom().nextInt(Medium.MAX_VALUE), pniIdentity.privateKey)
+        }
+        devicePniLastResortKyberPreKeys[deviceId] = KyberPreKeyEntity(lastResortKyberPreKeyRecord.id, lastResortKyberPreKeyRecord.keyPair.publicKey, lastResortKyberPreKeyRecord.signature)
+
         // Registration Ids
         var pniRegistrationId = if (deviceId == primaryDeviceId && pniUpdateMode) {
           SignalStore.account().pniRegistrationId
@@ -357,7 +373,9 @@ class ChangeNumberRepository(
           val pniChangeNumber = SyncMessage.PniChangeNumber.newBuilder()
             .setIdentityKeyPair(pniIdentity.serialize().toProtoByteString())
             .setSignedPreKey(signedPreKeyRecord.serialize().toProtoByteString())
+            .setLastResortKyberPreKey(lastResortKyberPreKeyRecord.serialize().toProtoByteString())
             .setRegistrationId(pniRegistrationId)
+            .setNewE164(newE164)
             .build()
 
           deviceMessages += messageSender.getEncryptedSyncPniChangeNumberMessage(deviceId, pniChangeNumber)
@@ -372,6 +390,7 @@ class ChangeNumberRepository(
       pniIdentity.publicKey,
       deviceMessages,
       devicePniSignedPreKeys.mapKeys { it.key.toString() },
+      devicePniLastResortKyberPreKeys.mapKeys { it.key.toString() },
       pniRegistrationIds.mapKeys { it.key.toString() }
     )
 
diff --git a/libsignal/service/src/main/java/org/whispersystems/signalservice/api/account/ChangePhoneNumberRequest.java b/libsignal/service/src/main/java/org/whispersystems/signalservice/api/account/ChangePhoneNumberRequest.java
index 8910e177e2..15aba7abd6 100644
--- a/libsignal/service/src/main/java/org/whispersystems/signalservice/api/account/ChangePhoneNumberRequest.java
+++ b/libsignal/service/src/main/java/org/whispersystems/signalservice/api/account/ChangePhoneNumberRequest.java
@@ -6,6 +6,7 @@ import com.fasterxml.jackson.databind.annotation.JsonSerialize;
 
 import org.signal.libsignal.protocol.IdentityKey;
 import org.whispersystems.signalservice.api.push.SignedPreKeyEntity;
+import org.whispersystems.signalservice.internal.push.KyberPreKeyEntity;
 import org.whispersystems.signalservice.internal.push.OutgoingPushMessage;
 import org.whispersystems.signalservice.internal.util.JsonUtil;
 
@@ -36,6 +37,9 @@ public final class ChangePhoneNumberRequest {
   @JsonProperty
   private Map<String, SignedPreKeyEntity> devicePniSignedPrekeys;
 
+  @JsonProperty("devicePniPqLastResortPrekeys")
+  private Map<String, KyberPreKeyEntity> devicePniLastResortKyberPrekeys;
+
   @JsonProperty
   private Map<String, Integer> pniRegistrationIds;
 
@@ -49,16 +53,18 @@ public final class ChangePhoneNumberRequest {
                                   IdentityKey pniIdentityKey,
                                   List<OutgoingPushMessage> deviceMessages,
                                   Map<String, SignedPreKeyEntity> devicePniSignedPrekeys,
+                                  Map<String, KyberPreKeyEntity> devicePniLastResortKyberPrekeys,
                                   Map<String, Integer> pniRegistrationIds)
   {
-    this.sessionId              = sessionId;
-    this.recoveryPassword       = recoveryPassword;
-    this.number                 = number;
-    this.registrationLock       = registrationLock;
-    this.pniIdentityKey         = pniIdentityKey;
-    this.deviceMessages         = deviceMessages;
-    this.devicePniSignedPrekeys = devicePniSignedPrekeys;
-    this.pniRegistrationIds     = pniRegistrationIds;
+    this.sessionId                       = sessionId;
+    this.recoveryPassword                = recoveryPassword;
+    this.number                          = number;
+    this.registrationLock                = registrationLock;
+    this.pniIdentityKey                  = pniIdentityKey;
+    this.deviceMessages                  = deviceMessages;
+    this.devicePniSignedPrekeys          = devicePniSignedPrekeys;
+    this.devicePniLastResortKyberPrekeys = devicePniLastResortKyberPrekeys;
+    this.pniRegistrationIds              = pniRegistrationIds;
   }
 
   public String getNumber() {
diff --git a/libsignal/service/src/main/proto/SignalService.proto b/libsignal/service/src/main/proto/SignalService.proto
index a0bbbadc2b..7baf8f8096 100644
--- a/libsignal/service/src/main/proto/SignalService.proto
+++ b/libsignal/service/src/main/proto/SignalService.proto
@@ -590,9 +590,12 @@ message SyncMessage {
   }
 
   message PniChangeNumber {
-    optional bytes  identityKeyPair = 1; // Serialized libsignal-client IdentityKeyPair
-    optional bytes  signedPreKey    = 2; // Serialized libsignal-client SignedPreKeyRecord
-    optional uint32 registrationId  = 3;
+    optional bytes  identityKeyPair       = 1; // Serialized libsignal-client IdentityKeyPair
+    optional bytes  signedPreKey          = 2; // Serialized libsignal-client SignedPreKeyRecord
+    optional bytes  lastResortKyberPreKey = 5; // Serialized libsignal-client KyberPreKeyRecord
+    optional uint32 registrationId        = 3;
+    optional string newE164               = 4; // The e164 we have changed our number to
+    // Next ID: 6
   }
 
   message CallEvent {