diff --git a/chatbuf.proto b/chatbuf.proto
index 351afd0..c8e4d35 100644
--- a/chatbuf.proto
+++ b/chatbuf.proto
@@ -11,5 +11,5 @@
   }
   required ChatMessageType type = 3 [default = CHAT];
   optional string data = 4;
-  optional int32 timestamp = 5;
+  required int32 timestamp = 5;
 }