diff --git a/internal/locate/region_request.go b/internal/locate/region_request.go
index 8e3aca793..c8e97c8bf 100644
--- a/internal/locate/region_request.go
+++ b/internal/locate/region_request.go
@@ -371,6 +371,7 @@ func (state *accessKnownLeader) onNoLeader(selector *replicaSelector) {
 // the leader will be updated to replicas[0] and give it another chance.
 type tryFollower struct {
 	stateBase
+	// if the leader is unavailable, but it still holds the leadership, fallbackFromLeader is true and replica read is enabled.
 	fallbackFromLeader bool
 	leaderIdx          AccessIndex
 	lastIdx            AccessIndex