diff --git a/src/kernel_services/ast_queries/cil_datatype.mli b/src/kernel_services/ast_queries/cil_datatype.mli
index f83bc30afaad8b70869486bbfaa1ba8c473877fa..460f01de5cb0fe57a65b3123cf6e77d965a652c1 100644
--- a/src/kernel_services/ast_queries/cil_datatype.mli
+++ b/src/kernel_services/ast_queries/cil_datatype.mli
@@ -215,7 +215,7 @@ module TypNoUnroll: S_with_collections_pretty with type t = typ
 
 module Typeinfo: S_with_collections with type t = typeinfo
 
-module Varinfo_Id: Hptmap.Id_Datatype
+module Varinfo_Id: Hptmap.Id_Datatype with type t = varinfo
 
 (** @plugin development guide *)
 module Varinfo: sig