diff --git a/op-service/eth/id.go b/op-service/eth/id.go
index 7aa20cf45..7c51cdf6a 100644
--- a/op-service/eth/id.go
+++ b/op-service/eth/id.go
@@ -58,8 +58,8 @@ type L1BlockRef struct {
 	Hash       common.Hash `json:"hash"`
 	Number     uint64      `json:"number"`
 	ParentHash common.Hash `json:"parentHash"`
-	Time       uint64      `json:"timestamp"`
-	mTime      uint64      `json:"timestamp"` // millisecond representation
+	Time       uint64      `json:"timestamp"`   // second timestamp
+	mTime      uint64      `json:"msTimestamp"` // support millisecond
 }
 
 func (id L1BlockRef) MilliTimestamp() uint64 {