diff --git a/src/database.ml b/src/database.ml
index a9753418..bb7e5ec5 100644
--- a/src/database.ml
+++ b/src/database.ml
@@ -1,3 +1,7 @@
+(* TODO
+   GNU Taler db-events
+   https://git.gnunet.org/gana.git/tree/gnu-taler-db-events/registry.rec *)
+
 let test req server _ =
   let pool = Vif.Server.device Devices.caqti server in
   let query =