diff --git a/scripts/storage.sql b/scripts/storage.sql
index 939ed1272..b4d2b859d 100644
--- a/scripts/storage.sql
+++ b/scripts/storage.sql
@@ -75,7 +75,7 @@ CREATE TABLE IF NOT EXISTS TreeHead(
   FOREIGN KEY(TreeId) REFERENCES Trees(TreeId) ON DELETE CASCADE
 );
 
-CREATE UNIQUE INDEX TreeHeadRevisionIdx
+CREATE UNIQUE INDEX IF NOT EXISTS TreeHeadRevisionIdx
   ON TreeHead(TreeId, TreeRevision);
 
 -- ---------------------------------------------