diff --git a/pkgs/development/compilers/reason/default.nix b/pkgs/development/compilers/reason/default.nix
index 715b000f323d..5ade7fd6fbae 100644
--- a/pkgs/development/compilers/reason/default.nix
+++ b/pkgs/development/compilers/reason/default.nix
@@ -1,23 +1,24 @@
 { stdenv, makeWrapper, fetchFromGitHub, ocaml, findlib, dune
-, menhir, merlin-extend, ppx_tools_versioned, utop
+, menhir, merlin-extend, ppx_tools_versioned, utop, cppo
+, ocaml_lwt
 }:
 
 stdenv.mkDerivation rec {
   name = "ocaml${ocaml.version}-reason-${version}";
-  version = "3.3.7";
+  version = "3.5.0";
 
   src = fetchFromGitHub {
     owner = "facebook";
     repo = "reason";
-    rev = "4d20e5b535c29c5ef1283e65958b32996e449e5a";
-    sha256 = "0f3pb61wg58g8f3wcnp1h4gpmnwmp7bq0cnqdfwldmh9cs0dqyfk";
+    rev = "ea207004e021efef5a92ecd011d9d5b9b16bbded";
+    sha256 = "0cdjy7sw15rlk63prrwy8lavqrz8fqwsgwr19ihvj99x332r98kk";
   };
 
   nativeBuildInputs = [ makeWrapper ];
 
   propagatedBuildInputs = [ menhir merlin-extend ppx_tools_versioned ];
 
-  buildInputs = [ ocaml findlib dune utop menhir ];
+  buildInputs = [ ocaml findlib dune cppo utop menhir ];
 
   buildFlags = [ "build" ]; # do not "make tests" before reason lib is installed
 
@@ -26,6 +27,7 @@ stdenv.mkDerivation rec {
   postInstall = ''
     wrapProgram $out/bin/rtop \
       --prefix PATH : "${utop}/bin" \
+      --set CAML_LD_LIBRARY_PATH ${ocaml_lwt}/lib/ocaml/${ocaml.version}/site-lib:$CAML_LD_LIBRARY_PATH \
       --set OCAMLPATH $out/lib/ocaml/${ocaml.version}/site-lib:$OCAMLPATH
   '';