diff --git a/sidekick.opam b/sidekick.opam
index 49f9e558..074e09b2 100644
--- a/sidekick.opam
+++ b/sidekick.opam
@@ -11,10 +11,10 @@ build: [
   ["dune" "runtest" "-p" name "-j" jobs] {with-test}
 ]
 depends: [
-  "dune" { >= "1.1" }
-  "containers" { >= "3.0" & < "4.0" }
+  "dune" { >= "2.0" }
+  "containers" { >= "3.6" & < "4.0" }
   "iter" { >= "1.0" & < "2.0" }
-  "ocaml" { >= "4.04" }
+  "ocaml" { >= "4.08" }
   "zarith" { with-test }
   "alcotest" {with-test}
   "odoc" {with-doc}
diff --git a/src/cc/Sidekick_cc.ml b/src/cc/Sidekick_cc.ml
index 79adf3f9..20d3d418 100644
--- a/src/cc/Sidekick_cc.ml
+++ b/src/cc/Sidekick_cc.ml
@@ -308,7 +308,6 @@ module Make (A: CC_ARG)
     mutable on_conflict: ev_on_conflict list;
     mutable on_propagate: ev_on_propagate list;
     mutable on_is_subterm : ev_on_is_subterm list;
-    stat: Stat.t;
     count_conflict: int Stat.counter;
     count_props: int Stat.counter;
     count_merge: int Stat.counter;
@@ -639,7 +638,7 @@ module Make (A: CC_ARG)
          T_tbl.remove cc.tbl t);
     (* add term to the table *)
     T_tbl.add cc.tbl t n;
-    if CCOpt.is_some sig0 then (
+    if Option.is_some sig0 then (
       (* [n] might be merged with other equiv classes *)
       push_pending cc n;
     );
@@ -1164,7 +1163,6 @@ module Make (A: CC_ARG)
       undo=Backtrack_stack.create();
       true_;
       false_;
-      stat;
       field_marked_explain;
       count_conflict=Stat.mk_int stat "cc.conflicts";
       count_props=Stat.mk_int stat "cc.propagations";
diff --git a/src/drup/sidekick_drup.ml b/src/drup/sidekick_drup.ml
index d21efe14..cdd29e28 100644
--- a/src/drup/sidekick_drup.ml
+++ b/src/drup/sidekick_drup.ml
@@ -185,7 +185,6 @@ module Make() : S = struct
     val del_clause : t -> Clause.t -> unit
   end = struct
     type t = {
-      cstore: Clause.store;
       assign: Atom.Assign.t; (* atom -> is_true(atom) *)
       trail: Atom.Stack.t; (* current assignment *)
       mutable trail_ptr : int; (* offset in trail for propagation *)
@@ -193,10 +192,9 @@ module Make() : S = struct
       watches: Clause.t Vec.t Atom.Map.t; (* atom -> clauses it watches *)
     }
 
-    let create cstore : t =
+    let create _cstore : t =
       { trail=Atom.Stack.create();
         trail_ptr = 0;
-        cstore;
         active_clauses=Clause.Tbl.create 32;
         assign=Atom.Assign.create();
         watches=Atom.Map.create();
diff --git a/src/intsolver/sidekick_intsolver.ml b/src/intsolver/sidekick_intsolver.ml
index 853a1817..dea33cc6 100644
--- a/src/intsolver/sidekick_intsolver.ml
+++ b/src/intsolver/sidekick_intsolver.ml
@@ -173,7 +173,7 @@ module Make(A : ARG)
       while Z.(!n <= n0) do
         if is_prime !n then k !n
       done
-  end
+  end [@@warning "-60"]
 
 
   module Op = struct
diff --git a/src/lia/intf_lia.ml b/src/lia/intf_lia.ml
index 6e213a2f..6719f237 100644
--- a/src/lia/intf_lia.ml
+++ b/src/lia/intf_lia.ml
@@ -1,5 +1,4 @@
 
-open Sidekick_core
 
 module type RATIONAL = Sidekick_arith.RATIONAL
 module type INT = Sidekick_arith.INT
diff --git a/src/lra/sidekick_arith_lra.ml b/src/lra/sidekick_arith_lra.ml
index 53aca04d..72eb5be1 100644
--- a/src/lra/sidekick_arith_lra.ml
+++ b/src/lra/sidekick_arith_lra.ml
@@ -157,7 +157,6 @@ module Make(A : ARG) : S with module A = A = struct
       let mk_lit _ _ _ = assert false
     end)
   module Subst = SimpSolver.Subst
-  module Q_tbl = CCHashtbl.Make(A.Q)
 
   module Comb_map = CCMap.Make(LE_.Comb)
 
@@ -243,7 +242,6 @@ module Make(A : ARG) : S with module A = A = struct
     mutable encoded_le: T.t Comb_map.t; (* [le] -> var encoding [le] *)
     simplex: SimpSolver.t;
     mutable last_res: SimpSolver.result option;
-    stat_th_comb: int Stat.counter;
   }
 
   let create ?(stat=Stat.create()) (si:SI.t) : state =
@@ -262,7 +260,6 @@ module Make(A : ARG) : S with module A = A = struct
       encoded_le=Comb_map.empty;
       simplex=SimpSolver.create ~stat ();
       last_res=None;
-      stat_th_comb=Stat.mk_int stat "lra.th-comb";
     }
 
   let[@inline] reset_res_ (self:state) : unit =
@@ -537,8 +534,6 @@ module Make(A : ARG) : S with module A = A = struct
       )
     | _ -> None
 
-  module Q_map = CCMap.Make(A.Q)
-
   (* raise conflict from certificate *)
   let fail_with_cert si acts cert : 'a =
     Profile.with1 "lra.simplex.check-cert" SimpSolver._check_cert cert;
@@ -624,7 +619,7 @@ module Make(A : ARG) : S with module A = A = struct
   (* evaluate a term directly, as a variable *)
   let eval_in_subst_ subst t = match A.view_as_lra t with
     | LRA_const n -> n
-    | _ -> Subst.eval subst t |> CCOpt.get_or ~default:A.Q.zero
+    | _ -> Subst.eval subst t |> Option.value ~default:A.Q.zero
 
   (* evaluate a linear expression *)
   let eval_le_in_subst_ subst (le:LE.t) =
@@ -754,7 +749,7 @@ module Make(A : ARG) : S with module A = A = struct
         begin match A.view_as_lra t with
           | LRA_const n -> Some n (* always eval constants to themselves *)
           | _ -> SimpSolver.V_map.get t m
-        end |> CCOpt.map (t_const self)
+        end |> Option.map (t_const self)
       | _ -> None
     end
 
diff --git a/src/sat/Solver.ml b/src/sat/Solver.ml
index 54c32636..d6cf8691 100644
--- a/src/sat/Solver.ml
+++ b/src/sat/Solver.ml
@@ -730,10 +730,6 @@ module Make(Plugin : PLUGIN)
     (* learnt clauses (tautologies true at any time, whatever the user level).
        GC'd regularly. *)
 
-    clauses_dead : CVec.t;
-    (* dead clauses, to be removed at next GC.
-       invariant: all satisfy [Clause.dead store c]. *)
-
     clause_pools : clause_pool Vec.t;
     (* custom clause pools *)
 
@@ -754,7 +750,7 @@ module Make(Plugin : PLUGIN)
     var_levels : VecSmallInt.t;
     (* decision levels in [trail]  *)
 
-    mutable assumptions: AVec.t;
+    assumptions: AVec.t;
     (* current assumptions *)
 
     mutable th_head : int;
@@ -824,7 +820,6 @@ module Make(Plugin : PLUGIN)
         ~descr:(fun () -> "cp.learnt-clauses")
         ~max_size:max_clauses_learnt ();
     delayed_actions=Delayed_actions.create();
-    clauses_dead = CVec.create();
     clause_pools = Vec.create();
 
     to_clear=Vec.create();
diff --git a/src/simplex/linear_expr.ml b/src/simplex/linear_expr.ml
index 9873e93c..b381d931 100644
--- a/src/simplex/linear_expr.ml
+++ b/src/simplex/linear_expr.ml
@@ -146,7 +146,7 @@ module Make(C : COEFF)(Var : VAR) = struct
     }
 
     let compare c c' =
-      CCOrd.(compare c.op c'.op
+      CCOrd.(poly c.op c'.op
              <?> (Expr.compare, c.expr, c'.expr))
 
     let pp_op out o =
diff --git a/src/smt-solver/Sidekick_smt_solver.ml b/src/smt-solver/Sidekick_smt_solver.ml
index a667129d..c20e8554 100644
--- a/src/smt-solver/Sidekick_smt_solver.ml
+++ b/src/smt-solver/Sidekick_smt_solver.ml
@@ -88,7 +88,6 @@ module Make(A : ARG)
   module Term = T.Term
   module Lit = A.Lit
   type term = Term.t
-  type value = term
   type ty = Ty.t
   type proof = A.proof
   type proof_step = A.proof_step
@@ -354,8 +353,8 @@ module Make(A : ARG)
     let on_th_combination self f = self.on_th_combination <- f :: self.on_th_combination
     let on_preprocess self f = self.preprocess <- f :: self.preprocess
     let on_model ?ask ?complete self =
-      CCOpt.iter (fun f -> self.model_ask <- f :: self.model_ask) ask;
-      CCOpt.iter (fun f -> self.model_complete <- f :: self.model_complete) complete;
+      Option.iter (fun f -> self.model_ask <- f :: self.model_ask) ask;
+      Option.iter (fun f -> self.model_complete <- f :: self.model_complete) complete;
       ()
 
     let[@inline] raise_conflict self (acts:theory_actions) c proof : 'a =
@@ -472,7 +471,7 @@ module Make(A : ARG)
         (* simplify a literal, then preprocess it *)
         let[@inline] simp_lit lit =
           let lit, pr = simplify_and_preproc_lit_ self lit in
-          CCOpt.iter (fun pr -> steps := pr :: !steps) pr;
+          Option.iter (fun pr -> steps := pr :: !steps) pr;
           lit
         in
         let c' = A.map simp_lit c in
@@ -1014,7 +1013,7 @@ module Make(A : ARG)
           (fun k->k "(@[sidekick.smt-solver: SAT@ actual: UNKNOWN@ :reason incomplete-fragment@])");
         Unknown Unknown.U_incomplete
 
-      | Sat_solver.Sat (module SAT) ->
+      | Sat_solver.Sat _ ->
         Log.debug 1 "(sidekick.smt-solver: SAT)";
 
         Log.debugf 5
diff --git a/src/smtlib/Process.ml b/src/smtlib/Process.ml
index ef33c043..5052c27b 100644
--- a/src/smtlib/Process.ml
+++ b/src/smtlib/Process.ml
@@ -156,8 +156,8 @@ let solve
   let should_stop = match time, memory with
     | None, None -> None
     | _ ->
-      let time = CCOpt.get_or ~default:3600. time in (* default: 1 hour *)
-      let memory = CCOpt.get_or ~default:4e9 memory in (* default: 4 GB *)
+      let time = Option.value ~default:3600. time in (* default: 1 hour *)
+      let memory = Option.value ~default:4e9 memory in (* default: 4 GB *)
       let stop _ _ =
         Sys.time () -. t1 > time ||
         (Gc.quick_stat()).Gc.major_words *. 8. > memory
diff --git a/src/th-bool-static/Sidekick_th_bool_static.ml b/src/th-bool-static/Sidekick_th_bool_static.ml
index 9c865d30..7b3db517 100644
--- a/src/th-bool-static/Sidekick_th_bool_static.ml
+++ b/src/th-bool-static/Sidekick_th_bool_static.ml
@@ -167,7 +167,7 @@ module Make(A : ARG) : S with module A = A = struct
       (* directly simplify [a] so that maybe we never will simplify one
          of the branches *)
       let a, prf_a = SI.Simplify.normalize_t simp a in
-      CCOpt.iter add_step_ prf_a;
+      Option.iter add_step_ prf_a;
       begin match A.view_as_bool a with
         | B_bool true ->
           add_step_eq t b ~using:(Iter.of_opt prf_a)