diff --git a/go/vt/binlog/binlogplayer/binlog_player.go b/go/vt/binlog/binlogplayer/binlog_player.go
index <HASH>..<HASH> 100644
--- a/go/vt/binlog/binlogplayer/binlog_player.go
+++ b/go/vt/binlog/binlogplayer/binlog_player.go
@@ -560,7 +560,7 @@ func CreateVReplicationTable() []string {
 // AlterVReplicationTable adds new columns to vreplication table
 var AlterVReplicationTable = []string{
 	"ALTER TABLE _vt.vreplication ADD COLUMN db_name VARBINARY(255) NOT NULL",
-	"ALTER TABLE _vt.vreplication MODIFY source BLOB NOT NULL",
+	"ALTER TABLE _vt.vreplication MODIFY source MEDIUMBLOB NOT NULL",
 	"ALTER TABLE _vt.vreplication ADD KEY workflow_idx (workflow(64))",
 	"ALTER TABLE _vt.vreplication ADD COLUMN rows_copied BIGINT(20) NOT NULL DEFAULT 0",
 	"ALTER TABLE _vt.vreplication ADD COLUMN tags VARBINARY(1024) NOT NULL DEFAULT ''",
Increase max vrepl source def size from <I>KiB to <I>MiB (#<I>)

This will allow us to avoid practical limits on the number of shard

and table definitions in workflows.