diff --git a/proto/kvrpcpb.proto b/proto/kvrpcpb.proto
index 03133bdaa..fac4b7335 100644
--- a/proto/kvrpcpb.proto
+++ b/proto/kvrpcpb.proto
@@ -786,6 +786,9 @@ message Context {
     // The source of the request, will be used as the tag of the metrics reporting.
     // This field can be set for any requests that require to report metrics with any extra labels.
     string request_source = 24;
+    
+    // The source of the current transaction.
+    uint32 txn_source = 25;
 }
 
 // The API version the server and the client is using.