diff --git a/src/plugins/server/states.ml b/src/plugins/server/states.ml
index 9b388ef7387d88df07088c0bc54a366c786e53bd..9d3d39768162e50d08b6c0a408277000f7a09e13 100644
--- a/src/plugins/server/states.ml
+++ b/src/plugins/server/states.ml
@@ -124,7 +124,10 @@ type 'a array = {
   key : 'a -> string ;
   iter : ('a -> unit) -> unit ;
   getter : (string * ('a -> json)) list ;
-  mutable current : 'a content option ; (* fast access *)
+  (* [LC+JS]
+     The two following fields allow to keep an array in sync
+     with the current project and still have a polymorphic data type. *)
+  mutable current : 'a content option ; (* fast access to current project *)
   projects : (string , 'a content) Hashtbl.t ; (* indexed by project *)
 }