diff --git a/protob/messages-bitcoin.proto b/protob/messages-bitcoin.proto
index 632d0be8b..7b1f89f0c 100644
--- a/protob/messages-bitcoin.proto
+++ b/protob/messages-bitcoin.proto
@@ -129,7 +129,7 @@ message SignTx {
     optional uint32 lock_time = 5 [default=0];          // transaction lock_time
     optional uint32 expiry = 6;                         // only for Decred and Zcash
     optional bool overwintered = 7;                     // only for Zcash
-    optional uint32 version_group_id = 4;               // only for Zcash, nVersionGroupId when overwintered is set
+    optional uint32 version_group_id = 8;               // only for Zcash, nVersionGroupId when overwintered is set
 }
 
 /**