diff --git a/src/findlib.ml b/src/findlib.ml
index 8ea0c0c7..e2fecae1 100644
--- a/src/findlib.ml
+++ b/src/findlib.ml
@@ -11,6 +11,14 @@ module Rule = struct
     ; value           : string
     }
 
+  let pp fmt { preds_required; preds_forbidden; value } =
+    Fmt.record fmt
+      [ "preds_required", Fmt.const Ps.pp preds_required
+      ; "preds_forbidden", Fmt.const Ps.pp preds_forbidden
+      ; "value", Fmt.const (fun fmt -> Format.fprintf fmt "%S") value
+      ]
+
+
   let formal_predicates_count t =
     Ps.cardinal t.preds_required + Ps.cardinal t.preds_forbidden
 
@@ -45,6 +53,12 @@ module Rules = struct
     ; add_rules : Rule.t list
     }
 
+  let pp fmt { set_rules; add_rules } =
+    Fmt.record fmt
+      [ "set_rules", (fun fmt () -> Fmt.ocaml_list Rule.pp fmt set_rules)
+      ; "add_rules", (fun fmt () -> Fmt.ocaml_list Rule.pp fmt add_rules)
+      ]
+
   let interpret t ~preds =
     let rec find_set_rule = function
       | [] -> None
@@ -92,6 +106,15 @@ module Config = struct
     ; preds : Ps.t
     }
 
+  let pp fmt { vars; preds } =
+    Fmt.record fmt
+      [ "vars"
+      , Fmt.const (Fmt.ocaml_list (Fmt.tuple Format.pp_print_string Rules.pp))
+          (String.Map.to_list vars)
+      ; "preds"
+      , Fmt.const Ps.pp preds
+      ]
+
   let load path ~toolchain ~context =
     let path = Path.extend_basename path ~suffix:".d" in
     let conf_file = Path.relative path (toolchain ^ ".conf") in
diff --git a/src/findlib.mli b/src/findlib.mli
index 535332ac..83875550 100644
--- a/src/findlib.mli
+++ b/src/findlib.mli
@@ -1,6 +1,6 @@
 (** Findlib database *)
 
-open Stdune
+open Import
 
 (** Findlib database *)
 type t
@@ -60,6 +60,9 @@ val dummy_package : t -> name:string -> Package.t
 
 module Config : sig
   type t
+
+  val pp : t Fmt.t
+
   val load : Path.t -> toolchain:string -> context:string -> t
   val get : t -> string -> string option
 
diff --git a/src/import.ml b/src/import.ml
index fd1640f2..ca2d0407 100644
--- a/src/import.ml
+++ b/src/import.ml
@@ -150,6 +150,9 @@ module Fmt = struct
       let pp_sep fmt () = Format.fprintf fmt "@,; " in
       Format.fprintf fmt "@[<hv>{ %a@ }@]"
         (Format.pp_print_list ~pp_sep pp) xs
+
+  let tuple ppfa ppfb fmt (a, b) =
+    Format.fprintf fmt "@[<hv>(%a, %a)@]" ppfa a ppfb b
 end
 
 (* This is ugly *)
diff --git a/src/interned.ml b/src/interned.ml
index 34111eb5..ac663573 100644
--- a/src/interned.ml
+++ b/src/interned.ml
@@ -9,6 +9,8 @@ module type S = sig
   module Set : sig
     include Set.S with type elt = t
     val make : string list -> t
+
+    val pp : t Fmt.t
   end
   module Map : Map.S with type key = t
   module Table : sig
@@ -72,11 +74,15 @@ module Make() = struct
 
   let to_string t = Table.get names t
 
+  let pp fmt t = Format.fprintf fmt "%S" (to_string t)
+
   module Set = struct
     include Int_set
 
     let make l =
       List.fold_left l ~init:empty ~f:(fun acc s -> add acc (make s))
+
+    let pp fmt (t : t) = Fmt.ocaml_list pp fmt (to_list t)
   end
 
   module Map = Int_map
diff --git a/src/interned.mli b/src/interned.mli
index 14aee82d..613020bc 100644
--- a/src/interned.mli
+++ b/src/interned.mli
@@ -17,6 +17,8 @@ module type S = sig
     include Set.S with type elt = t
 
     val make : string list -> t
+
+    val pp : t Fmt.t
   end
 
   module Map : Map.S with type key = t