diff --git a/spanner/transaction.go b/spanner/transaction.go
index 654d5bc30342..8bce7cc1e710 100644
--- a/spanner/transaction.go
+++ b/spanner/transaction.go
@@ -186,7 +186,8 @@ type ReadOptions struct {
 	// An option to control the order in which rows are returned from a read.
 	OrderBy sppb.ReadRequest_OrderBy
 
-	// A lock hint mechanism to use for this request.
+	// A lock hint mechanism to use for this request. This setting is only applicable for
+	// read-write transaction as as read-only transactions do not take locks.
 	LockHint sppb.ReadRequest_LockHint
 }