diff --git a/protos/SignalService.proto b/protos/SignalService.proto
index d28f64aa26a1..a8c9b18187e7 100644
--- a/protos/SignalService.proto
+++ b/protos/SignalService.proto
@@ -227,6 +227,11 @@ message DataMessage {
     //}
   }
 
+  message GroupCallUpdate {
+    // Currently just a sentinel message indicating that a client should
+    // fetch updated group call state.
+  }
+
   enum ProtocolVersion {
     option allow_alias = true;
 
@@ -257,6 +262,7 @@ message DataMessage {
   optional Reaction           reaction                = 16;
   optional Delete             delete                  = 17;
   repeated BodyRange          bodyRanges              = 18;
+  optional GroupCallUpdate    groupCallUpdate         = 19;
 }
 
 message NullMessage {
diff --git a/ts/textsecure.d.ts b/ts/textsecure.d.ts
index ab80c5ff35ab..b42b9ae758e8 100644
--- a/ts/textsecure.d.ts
+++ b/ts/textsecure.d.ts
@@ -576,6 +576,7 @@ export declare class DataMessageClass {
   reaction?: DataMessageClass.Reaction;
   delete?: DataMessageClass.Delete;
   bodyRanges?: Array<DataMessageClass.BodyRange>;
+  groupCallUpdate?: DataMessageClass.GroupCallUpdate;
 }
 
 // Note: we need to use namespaces to express nested classes in Typescript
@@ -648,6 +649,8 @@ export declare namespace DataMessageClass {
     stickerId?: number;
     data?: AttachmentPointerClass;
   }
+
+  class GroupCallUpdate {}
 }
 
 // Note: we need to use namespaces to express nested classes in Typescript