diff --git a/src/dune_pkg/dependency_formula.ml b/src/dune_pkg/dependency_formula.ml
index 9b66ea156aa..a66e6dc8a0c 100644
--- a/src/dune_pkg/dependency_formula.ml
+++ b/src/dune_pkg/dependency_formula.ml
@@ -33,50 +33,6 @@ let rec remove_packages v pkgs =
     Or (l, r)
 ;;
 
-let rec is_post_filter filter =
-  match (filter : OpamTypes.filter) with
-  | FBool _ -> false
-  | FString _ -> false
-  | FIdent (_, var, _) ->
-    (match OpamVariable.to_string var with
-     | "post" -> true
-     | _ -> false)
-  | FOp (l, _relop, r) -> is_post_filter l || is_post_filter r
-  | FAnd (l, r) | FOr (l, r) -> is_post_filter l || is_post_filter r
-  | FNot filter -> not (is_post_filter filter)
-  | FDefined filter -> is_post_filter filter
-  | FUndef filter -> not (is_post_filter filter)
-;;
-
-let is_post_foc filter_or_constraint =
-  match (filter_or_constraint : OpamTypes.filter OpamTypes.filter_or_constraint) with
-  | Filter filter -> is_post_filter filter
-  | Constraint _ -> false
-;;
-
-let is_post condition =
-  condition |> OpamFormula.formula_to_cnf |> List.exists ~f:(List.exists ~f:is_post_foc)
-;;
-
-let reachable_dependencies v =
-  let rec loop v =
-    match (v : OpamTypes.filtered_formula) with
-    | Empty -> Package_name.Set.empty
-    | Atom (name, condition) ->
-      (match is_post condition with
-       | true -> Package_name.Set.empty
-       | false ->
-         let name = name |> OpamPackage.Name.to_string |> Package_name.of_string in
-         Package_name.Set.singleton name)
-    | Block b -> loop b
-    | And (l, r) | Or (l, r) ->
-      let l = loop l in
-      let r = loop r in
-      Package_name.Set.union l r
-  in
-  loop v
-;;
-
 let rec any_package_name v =
   match (v : OpamTypes.filtered_formula) with
   | Empty -> None
diff --git a/src/dune_pkg/dependency_formula.mli b/src/dune_pkg/dependency_formula.mli
index 885b6aa0e37..073e9289242 100644
--- a/src/dune_pkg/dependency_formula.mli
+++ b/src/dune_pkg/dependency_formula.mli
@@ -26,7 +26,3 @@ val has_entries : t -> bool
 (** Returns the [Package_name.t] of a dependency from the formula, if it
     exists. *)
 val any_package_name : t -> Package_name.t option
-
-(** Returns all dependency names that can be found in the formula, no matter
-    whether they can be satisfied or not *)
-val reachable_dependencies : t -> Package_name.Set.t
diff --git a/src/dune_pkg/opam_solver.ml b/src/dune_pkg/opam_solver.ml
index 1074337c240..b8edb8f9610 100644
--- a/src/dune_pkg/opam_solver.ml
+++ b/src/dune_pkg/opam_solver.ml
@@ -783,8 +783,21 @@ let reject_unreachable_packages =
     loop roots;
     !seen
   in
-  fun ~local_packages ~pkgs_by_name ->
+  fun solver_env ~local_packages ~pkgs_by_name ->
     let roots = Package_name.Map.keys local_packages in
+    let pkgs_by_version =
+      Package_name.Map.merge pkgs_by_name local_packages ~f:(fun name lhs rhs ->
+        match lhs, rhs with
+        | None, None -> assert false
+        | Some _, Some _ ->
+          Code_error.raise
+            "package is both local and returned by solver"
+            [ "name", Package_name.to_dyn name ]
+        | Some (lock_dir_pkg : Lock_dir.Pkg.t), None -> Some lock_dir_pkg.info.version
+        | None, Some _pkg ->
+          let version = Package_version.of_string "dev" in
+          Some version)
+    in
     let pkgs_by_name =
       Package_name.Map.merge pkgs_by_name local_packages ~f:(fun name lhs rhs ->
         match lhs, rhs with
@@ -795,10 +808,28 @@ let reject_unreachable_packages =
             [ "name", Package_name.to_dyn name ]
         | Some (pkg : Lock_dir.Pkg.t), None -> Some (List.map pkg.depends ~f:snd)
         | None, Some (pkg : Local_package.For_solver.t) ->
+          let formula = pkg.dependencies |> Dependency_formula.to_filtered_formula in
+          (* Use `dev` because at this point we don't have any version *)
+          let opam_package =
+            OpamPackage.of_string (sprintf "%s.dev" (Package_name.to_string pkg.name))
+          in
+          let env = add_self_to_filter_env opam_package (Solver_env.to_env solver_env) in
+          let resolved =
+            Resolve_opam_formula.filtered_formula_to_package_names
+              env
+              ~with_test:true
+              pkgs_by_version
+              formula
+          in
           let deps =
-            pkg.dependencies
-            |> Dependency_formula.reachable_dependencies
-            |> Package_name.Set.to_list
+            match resolved with
+            | Ok { regular; post = _ } ->
+              (* discard post deps *)
+              regular
+            | Error _ ->
+              Code_error.raise
+                "can't find a valid solution for the dependencies"
+                [ "name", Package_name.to_dyn pkg.name ]
           in
           let depopts =
             List.filter_map pkg.depopts ~f:(fun (d : Package_dependency.t) ->
@@ -914,7 +945,9 @@ let solve_lock_dir
                       (Package_name.to_string name)
                       (Package_name.to_string dep_name)
                   ]));
-        let reachable = reject_unreachable_packages ~local_packages ~pkgs_by_name in
+        let reachable =
+          reject_unreachable_packages solver_env ~local_packages ~pkgs_by_name
+        in
         let pkgs_by_name =
           Package_name.Map.filteri pkgs_by_name ~f:(fun name _ ->
             Package_name.Set.mem reachable name)