diff --git a/app/src/main/java/org/thoughtcrime/securesms/messages/MessageDecryptor.kt b/app/src/main/java/org/thoughtcrime/securesms/messages/MessageDecryptor.kt
index 42f564631e..57d6b7d5df 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/messages/MessageDecryptor.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/messages/MessageDecryptor.kt
@@ -395,7 +395,7 @@ object MessageDecryptor {
     val aciAddress = SignalProtocolAddress(aci.toString(), deviceId)
     val pniAddress = SignalProtocolAddress(pni.toString(), deviceId)
     val aciIdentity = protocolStore.getAciStore().getIdentity(aciAddress)
-    val pniIdentity = protocolStore.getAciStore().getIdentity(pniAddress)
+    var pniIdentity = protocolStore.getAciStore().getIdentity(pniAddress)
 
     if (aciIdentity == null) {
       Log.w(TAG, "${logPrefix(envelope, aci)}[validatePniSignature] No identity found for ACI address $aciAddress")
@@ -404,7 +404,18 @@ object MessageDecryptor {
 
     if (pniIdentity == null) {
       Log.w(TAG, "${logPrefix(envelope, aci)}[validatePniSignature] No identity found for PNI address $pniAddress")
-      return
+      if (deviceId != SignalServiceAddress.DEFAULT_DEVICE_ID) {
+        pniIdentity = protocolStore.getAciStore().getIdentity(SignalProtocolAddress(pni.toString(), SignalServiceAddress.DEFAULT_DEVICE_ID))
+
+        if (pniIdentity != null) {
+          Log.w(TAG, "${logPrefix(envelope, aci)}[validatePniSignature] Found PNI identity when looking up device 1. Using that.")
+        } else {
+          Log.w(TAG, "${logPrefix(envelope, aci)}[validatePniSignature] No PNI identity when looking up device 1 either.")
+          return
+        }
+      } else {
+        return
+      }
     }
 
     if (pniIdentity.verifyAlternateIdentity(aciIdentity, pniSignatureMessage.signature!!.toByteArray())) {
diff --git a/app/src/main/java/org/thoughtcrime/securesms/messages/SyncMessageProcessor.kt b/app/src/main/java/org/thoughtcrime/securesms/messages/SyncMessageProcessor.kt
index 602ab61527..e168112874 100644
--- a/app/src/main/java/org/thoughtcrime/securesms/messages/SyncMessageProcessor.kt
+++ b/app/src/main/java/org/thoughtcrime/securesms/messages/SyncMessageProcessor.kt
@@ -6,6 +6,9 @@ import com.mobilecoin.lib.exceptions.SerializationException
 import okio.ByteString
 import org.signal.core.util.Hex
 import org.signal.core.util.orNull
+import org.signal.libsignal.protocol.IdentityKey
+import org.signal.libsignal.protocol.InvalidKeyException
+import org.signal.libsignal.protocol.SignalProtocolAddress
 import org.signal.libsignal.protocol.util.Pair
 import org.signal.ringrtc.CallException
 import org.signal.ringrtc.CallLinkRootKey
@@ -96,6 +99,7 @@ import org.whispersystems.signalservice.api.messages.SignalServiceAttachmentPoin
 import org.whispersystems.signalservice.api.push.DistributionId
 import org.whispersystems.signalservice.api.push.ServiceId
 import org.whispersystems.signalservice.api.push.ServiceId.ACI
+import org.whispersystems.signalservice.api.push.ServiceId.PNI
 import org.whispersystems.signalservice.api.push.SignalServiceAddress
 import org.whispersystems.signalservice.api.storage.StorageKey
 import org.whispersystems.signalservice.internal.push.Content
@@ -169,6 +173,8 @@ object SyncMessageProcessor {
     log(envelope.timestamp!!, "Processing sent transcript for message with ID ${sent.timestamp!!}")
 
     try {
+      handlePniIdentityKeys(envelope, sent)
+
       if (sent.storyMessage != null || sent.storyMessageRecipients.isNotEmpty()) {
         handleSynchronizeSentStoryMessage(envelope, sent)
         return
@@ -246,6 +252,34 @@ object SyncMessageProcessor {
     }
   }
 
+  private fun handlePniIdentityKeys(envelope: Envelope, sent: Sent) {
+    for (status in sent.unidentifiedStatus) {
+      if (status.destinationIdentityKey == null) {
+        continue
+      }
+
+      val pni = PNI.parsePrefixedOrNull(status.destinationServiceId)
+      if (pni == null) {
+        continue
+      }
+
+      val address = SignalProtocolAddress(pni.toString(), SignalServiceAddress.DEFAULT_DEVICE_ID)
+
+      if (ApplicationDependencies.getProtocolStore().aci().identities().getIdentity(address) != null) {
+        log(envelope.timestamp!!, "Ignoring identity on sent transcript for $pni because we already have one.")
+        continue
+      }
+
+      try {
+        log(envelope.timestamp!!, "Saving identity from sent transcript for $pni")
+        val identityKey = IdentityKey(status.destinationIdentityKey!!.toByteArray())
+        ApplicationDependencies.getProtocolStore().aci().identities().saveIdentity(address, identityKey)
+      } catch (e: InvalidKeyException) {
+        warn(envelope.timestamp!!, "Failed to deserialize identity key for $pni")
+      }
+    }
+  }
+
   private fun getSyncMessageDestination(message: Sent): Recipient {
     return if (message.message.hasGroupContext) {
       Recipient.externalPossiblyMigratedGroup(GroupId.v2(message.message!!.groupV2!!.groupMasterKey))
diff --git a/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java b/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java
index 411a449cd3..9104c81518 100644
--- a/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java
+++ b/libsignal-service/src/main/java/org/whispersystems/signalservice/api/SignalServiceMessageSender.java
@@ -7,6 +7,7 @@ package org.whispersystems.signalservice.api;
 
 import org.signal.core.util.Base64;
 import org.signal.libsignal.metadata.certificate.SenderCertificate;
+import org.signal.libsignal.protocol.IdentityKey;
 import org.signal.libsignal.protocol.IdentityKeyPair;
 import org.signal.libsignal.protocol.InvalidKeyException;
 import org.signal.libsignal.protocol.InvalidRegistrationIdException;
@@ -1399,9 +1400,21 @@ public class SignalServiceMessageSender {
     List<SyncMessage.Sent.UnidentifiedDeliveryStatus> unidentifiedDeliveryStatuses = new ArrayList<>(sendMessageResults.size());
     for (SendMessageResult result : sendMessageResults) {
       if (result.getSuccess() != null) {
+        ByteString identity = null;
+
+        if (result.getAddress().getServiceId() instanceof PNI) {
+          IdentityKey identityKey = aciStore.getIdentity(result.getAddress().getServiceId().toProtocolAddress(SignalServiceAddress.DEFAULT_DEVICE_ID));
+          if (identityKey != null) {
+            identity = ByteString.of(identityKey.getPublicKey().serialize());
+          } else {
+            Log.w(TAG, "[" + timestamp + "] Could not find an identity for PNI when sending sync message! " + result.getAddress().getServiceId());
+          }
+        }
+
         unidentifiedDeliveryStatuses.add(new SyncMessage.Sent.UnidentifiedDeliveryStatus.Builder()
                                                                                         .destinationServiceId(result.getAddress().getServiceId().toString())
                                                                                         .unidentified(result.getSuccess().isUnidentified())
+                                                                                        .destinationIdentityKey(identity)
                                                                                         .build());
       }
     }
diff --git a/libsignal-service/src/main/protowire/SignalService.proto b/libsignal-service/src/main/protowire/SignalService.proto
index 49ef328a6b..5e3db8375c 100644
--- a/libsignal-service/src/main/protowire/SignalService.proto
+++ b/libsignal-service/src/main/protowire/SignalService.proto
@@ -439,9 +439,11 @@ message Verified {
 message SyncMessage {
   message Sent {
     message UnidentifiedDeliveryStatus {
-      reserved      /*destinationE164*/ 1;
-      optional string destinationServiceId = 3;
-      optional bool   unidentified         = 2;
+      reserved        /*destinationE164*/      1;
+      optional string destinationServiceId   = 3;
+      optional bool   unidentified           = 2;
+      reserved        /*destinationPni*/       4;
+      optional bytes  destinationIdentityKey = 5;
     }
 
     message StoryMessageRecipient {
@@ -460,6 +462,8 @@ message SyncMessage {
     optional StoryMessage               storyMessage             = 8;
     repeated StoryMessageRecipient      storyMessageRecipients   = 9;
     optional EditMessage                editMessage              = 10;
+    reserved                            /*destinationPni*/         11;
+    // NEXT ID: 12
   }
 
   message Contacts {