diff --git a/.appveyor.yml b/.appveyor.yml
index 141f2e1..fcef6d2 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -14,9 +14,7 @@ install:
 
 build_script:
   - call %CYG_ROOT%\bin\bash.exe -l %APPVEYOR_BUILD_FOLDER%\appveyor-opam.sh
-  - call %CYG_ROOT%\bin\bash.exe -l -c 'opam pin 'opam pin add kicadsch.dev --kind=path . -n'
-  - call %CYG_ROOT%\bin\bash.exe -l -c 'opam pin 'opam pin add plotkicadsch.dev --kind=path . -n'
-  - call %CYG_ROOT%\bin\bash.exe -l -c 'opam install plotkicadsch.dev'
+  - call %CYG_ROOT%\bin\bash.exe -l -c 'opam install plotkicadsch'
   - mv %CYG_ROOT%\home\appveyor\.opam %APPVEYOR_BUILD_FOLDER%\opam
 
 artifacts:
diff --git a/plotkicadsch.opam b/plotkicadsch.opam
index 6e7cf6e..4451990 100644
--- a/plotkicadsch.opam
+++ b/plotkicadsch.opam
@@ -17,7 +17,7 @@ build: [
   [ "dune" "build" "-p" name "-j" jobs]
 ]
 depends: [
-  "ocaml" {>="4.07"}
+  "ocaml" {>="4.09"}
   "dune" {>= "1.0"}
   "kicadsch" {= version}
   "tyxml" {>= "4.0.0"}
diff --git a/plotkicadsch/src/gitFs.ml b/plotkicadsch/src/gitFs.ml
index 1c53c24..d2dd2eb 100644
--- a/plotkicadsch/src/gitFs.ml
+++ b/plotkicadsch/src/gitFs.ml
@@ -86,7 +86,7 @@ let make commitish =
 
     let find_dir_local t =
       let file_list = Store.Value.Tree.to_list t in
-      List.filter ~f:(fun entry -> entry.perm = `Dir) file_list
+      List.filter ~f:(fun entry -> let open Core_kernel.Poly in entry.perm = `Dir) file_list
 
     let rec recurse_dir ?dirname node pattern =
       let rename name = match dirname with
diff --git a/plotkicadsch/src/kicadDiff.ml b/plotkicadsch/src/kicadDiff.ml
index 2b0b3ab..744f37c 100644
--- a/plotkicadsch/src/kicadDiff.ml
+++ b/plotkicadsch/src/kicadDiff.ml
@@ -18,18 +18,6 @@ let fs_mod = function
   | GitFS r -> GitFs.make r
   | TrueFS r -> TrueFs.make r
 
-let ends_with e s =
-  let ls = String.length s in
-  let le = String.length e in
-  if ls < le then false
-  else
-    let rec loop s e i =
-      if i = le then true
-      else if s.[ls - le + i] <> e.[i] then false
-      else loop s e (i + 1)
-    in
-    loop s e 0
-
 module L = Kicadsch.MakeSchPainter (ListPainter.L)
 
 module LP = struct
@@ -45,7 +33,7 @@ module FSPainter (S : SchPainter) (F : Simple_FS) : sig
 
   val context_from : S.schContext Lwt.t -> S.schContext Lwt.t
 end = struct
-  let find_schematics () = F.list_files (ends_with ".sch")
+  let find_schematics () = F.list_files (String.is_suffix ~suffix:".sch")
 
   let process_file initctx filename =
     let parse c l = S.parse_line l c in
@@ -57,7 +45,7 @@ end = struct
     S.output_context endctx
 
   let find_libs () =
-    F.list_files (ends_with "-cache.lib") >|= List.map ~f:(fun (n, _) -> n)
+    F.list_files (String.is_suffix ~suffix:"-cache.lib") >|= List.map ~f:fst
 
   let read_libs initial_ctx lib_list =
     Lwt_list.fold_left_s
diff --git a/plotkicadsch/src/plotgitsch.ml b/plotkicadsch/src/plotgitsch.ml
index e1dc9d5..2925e85 100644
--- a/plotkicadsch/src/plotgitsch.ml
+++ b/plotkicadsch/src/plotgitsch.ml
@@ -7,7 +7,7 @@ let pp_fs out fs =
   Format.fprintf out "%s" (doc fs)
 
 let get_fs s =
-  if String.length s > 4 && String.sub s ~pos:0 ~len:4 = "dir:" then
+  if String.length s > 4 && String.equal (String.sub s ~pos:0 ~len:4) "dir:" then
     true_fs (String.sub s ~pos:4 ~len:(String.length s - 4))
   else git_fs s
 
diff --git a/plotkicadsch/src/trueFs.ml b/plotkicadsch/src/trueFs.ml
index e35009e..1a53ebc 100644
--- a/plotkicadsch/src/trueFs.ml
+++ b/plotkicadsch/src/trueFs.ml
@@ -7,7 +7,7 @@ let make rootname =
 
     let label = TrueFS rootname
 
-    let rootname = String.lstrip ~drop:(fun c -> c = '/') rootname
+    let rootname = String.lstrip ~drop:(Char.equal '/') rootname
     let rootlength = (String.length rootname) + 1
 
     let get_content filename =