diff --git a/storage/mysql/tree_storage.go b/storage/mysql/tree_storage.go
index 316784f1df..7047ff988a 100644
--- a/storage/mysql/tree_storage.go
+++ b/storage/mysql/tree_storage.go
@@ -34,7 +34,7 @@ import (
 
 // These statements are fixed
 const (
-	insertSubtreeMultiSQL = `REPLACE INTO Subtree(TreeId, SubtreeId, Nodes, SubtreeRevision) ` + placeholderSQL
+	insertSubtreeMultiSQL = `INSERT INTO Subtree(TreeId, SubtreeId, Nodes, SubtreeRevision) ` + placeholderSQL + ` ON DUPLICATE KEY UPDATE Nodes=VALUES(Nodes)`
 	insertTreeHeadSQL     = `INSERT INTO TreeHead(TreeId,TreeHeadTimestamp,TreeSize,RootHash,TreeRevision,RootSignature)
 		 VALUES(?,?,?,?,?,?)`