diff --git a/protos/SignalService.proto b/protos/SignalService.proto
index 6279e666c926..fb2b4c02b759 100644
--- a/protos/SignalService.proto
+++ b/protos/SignalService.proto
@@ -366,6 +366,12 @@ message SyncMessage {
     optional uint64 timestamp  = 2;
   }
 
+  message Viewed {
+    optional string senderE164 = 1;
+    optional string senderUuid = 3;
+    optional uint64 timestamp = 2;
+  }
+
   message Configuration {
     optional bool   readReceipts                   = 1;
     optional bool   unidentifiedDeliveryIndicators = 2;
@@ -431,6 +437,8 @@ message SyncMessage {
   optional FetchLatest            fetchLatest            = 12;
   optional Keys                   keys                   = 13;
   optional MessageRequestResponse messageRequestResponse = 14;
+  reserved                                                 15; // not yet added
+  repeated Viewed                 viewed                 = 16;
 }
 
 message AttachmentPointer {
diff --git a/ts/textsecure.d.ts b/ts/textsecure.d.ts
index ca88d2efdf85..45b680a1f2c0 100644
--- a/ts/textsecure.d.ts
+++ b/ts/textsecure.d.ts
@@ -1099,6 +1099,7 @@ export declare class SyncMessageClass {
   messageRequestResponse?: SyncMessageClass.MessageRequestResponse;
   fetchLatest?: SyncMessageClass.FetchLatest;
   keys?: SyncMessageClass.Keys;
+  viewed?: Array<SyncMessageClass.Viewed>;
 }
 
 // Note: we need to use namespaces to express nested classes in Typescript
@@ -1127,6 +1128,11 @@ export declare namespace SyncMessageClass {
     senderUuid: string | null;
     timestamp?: ProtoBigNumberType;
   }
+  class Viewed {
+    sender: string | null;
+    senderUuid: string | null;
+    timestamp?: ProtoBigNumberType;
+  }
   class Request {
     type?: number;
   }