diff --git a/libsignal/service/src/main/proto/SignalService.proto b/libsignal/service/src/main/proto/SignalService.proto
index e2cfea3e7e..ad5e5fb2dc 100644
--- a/libsignal/service/src/main/proto/SignalService.proto
+++ b/libsignal/service/src/main/proto/SignalService.proto
@@ -269,6 +269,7 @@ message DataMessage {
   optional Delete             delete                  = 17;
   repeated BodyRange          bodyRanges              = 18;
   optional GroupCallUpdate    groupCallUpdate         = 19;
+  reserved                 /* future use */             20;
 }
 
 message NullMessage {