diff --git a/dune-project b/dune-project
index 3d2898c..9cd64c9 100644
--- a/dune-project
+++ b/dune-project
@@ -52,8 +52,6 @@ This package uses 0install's solver algorithm with opam packages using
 the CUDF interface.
 ")
  (depends
-  fmt
-  cmdliner
   cudf
   (ocaml (>= 4.08.0))
   0install-solver))
diff --git a/lib-cudf/dune b/lib-cudf/dune
index b4bd1b8..2566cff 100644
--- a/lib-cudf/dune
+++ b/lib-cudf/dune
@@ -1,4 +1,4 @@
 (library
  (name opam_0install_cudf)
  (public_name opam-0install-cudf)
- (libraries cudf 0install-solver fmt))
+ (libraries cudf 0install-solver))
diff --git a/lib-cudf/model.ml b/lib-cudf/model.ml
index 8dc601d..e2435a9 100644
--- a/lib-cudf/model.ml
+++ b/lib-cudf/model.ml
@@ -39,18 +39,22 @@ module Make (Context : S.CONTEXT) = struct
     | Dummy                                     (* Used for diagnostics *)
 
   let rec pp_version f = function
-    | RealImpl impl -> Fmt.int f impl.pkg.Cudf.version
-    | Reject pkg -> Fmt.int f (snd pkg)
-    | VirtualImpl (_i, deps) -> Fmt.string f (String.concat "&" (List.map (fun d -> Fmt.to_to_string pp_role d.drole) deps))
-    | Dummy -> Fmt.string f "(no version)"
+    | RealImpl impl -> Format.pp_print_int f impl.pkg.Cudf.version
+    | Reject pkg -> Format.pp_print_int f (snd pkg)
+    | VirtualImpl (_i, deps) ->
+        Format.pp_print_string f
+          (String.concat "&" (List.map (fun d -> Format.asprintf "%a" pp_role d.drole) deps))
+    | Dummy -> Format.pp_print_string f "(no version)"
   and pp_impl f = function
-    | RealImpl impl -> Fmt.pf f "%s.%d" impl.pkg.Cudf.package impl.pkg.Cudf.version
-    | Reject pkg -> Fmt.pf f "%s.%d" (fst pkg) (snd pkg)
+    | RealImpl impl -> Format.fprintf f "%s.%d" impl.pkg.Cudf.package impl.pkg.Cudf.version
+    | Reject pkg -> Format.fprintf f "%s.%d" (fst pkg) (snd pkg)
     | VirtualImpl _ as x -> pp_version f x
-    | Dummy -> Fmt.string f "(no solution found)"
+    | Dummy -> Format.pp_print_string f "(no solution found)"
   and pp_role f = function
-    | Real t -> Fmt.string f t.name
-    | Virtual (_, impls) -> Fmt.pf f "%a" Fmt.(list ~sep:(unit "|") pp_impl) impls
+    | Real t -> Format.pp_print_string f t.name
+    | Virtual (_, impls) ->
+        Format.pp_print_string f
+          (String.concat "|" (List.map (Format.asprintf "%a" pp_impl) impls))
 
   let pp_impl_long = pp_impl
 
@@ -244,10 +248,10 @@ module Make (Context : S.CONTEXT) = struct
 
   let string_of_restriction = function
     | { kind = `Prevent; expr = [] } -> "conflict with all versions"
-    | { kind = `Prevent; expr } -> Fmt.strf "not(%s)" (string_of_version_formula expr)
+    | { kind = `Prevent; expr } -> Format.asprintf "not(%s)" (string_of_version_formula expr)
     | { kind = `Ensure; expr } -> string_of_version_formula expr
 
-  let describe_problem _impl = Fmt.to_to_string Context.pp_rejection
+  let describe_problem _impl = Format.asprintf "%a" Context.pp_rejection
 
   let version = function
     | RealImpl impl -> Some (impl.pkg.Cudf.package, impl.pkg.Cudf.version)
diff --git a/lib-cudf/opam_0install_cudf.ml b/lib-cudf/opam_0install_cudf.ml
index 31d751e..d43d3b0 100644
--- a/lib-cudf/opam_0install_cudf.ml
+++ b/lib-cudf/opam_0install_cudf.ml
@@ -50,7 +50,7 @@ module Context = struct
     | Some (`Lt, v) -> "<"^string_of_int v
 
   let pp_rejection f = function
-    | UserConstraint (name, c) -> Fmt.pf f "Rejected by user-specified constraint %s%s" name (print_constr c)
+    | UserConstraint (name, c) -> Format.fprintf f "Rejected by user-specified constraint %s%s" name (print_constr c)
 end
 
 module Input = Model.Make(Context)
diff --git a/lib-cudf/s.ml b/lib-cudf/s.ml
index 700e24b..ddc7982 100644
--- a/lib-cudf/s.ml
+++ b/lib-cudf/s.ml
@@ -5,7 +5,7 @@ module type CONTEXT = sig
   (** A reason why a package can't be used as input to the solver. e.g. it is
       for a different platform, or conflicts with a user-provided constraint. *)
 
-  val pp_rejection : rejection Fmt.t
+  val pp_rejection : Format.formatter -> rejection -> unit
 
   val candidates : t -> Cudf_types.pkgname -> (Cudf_types.version * (Cudf.package, rejection) result) list
   (** [candidates t name] is the list of available versions of [name], in order
diff --git a/opam-0install-cudf.opam b/opam-0install-cudf.opam
index e411a2f..1a0cc07 100644
--- a/opam-0install-cudf.opam
+++ b/opam-0install-cudf.opam
@@ -21,8 +21,6 @@ doc: "https://ocaml-opam.github.io/opam-0install-solver/"
 bug-reports: "https://github.com/ocaml-opam/opam-0install-solver/issues"
 depends: [
   "dune" {>= "2.0"}
-  "fmt"
-  "cmdliner"
   "cudf"
   "ocaml" {>= "4.08.0"}
   "0install-solver"