diff --git a/pkgs/development/ocaml-modules/ppx_tools/default.nix b/pkgs/development/ocaml-modules/ppx_tools/default.nix
index b6a6039a4fa..62aa97de5fa 100644
--- a/pkgs/development/ocaml-modules/ppx_tools/default.nix
+++ b/pkgs/development/ocaml-modules/ppx_tools/default.nix
@@ -7,6 +7,10 @@ let param = {
   "4.03.0" = {
     version = "5.0+4.03.0";
     sha256 = "061v1fl5z7z3ywi4ppryrlcywnvnqbsw83ppq72qmkc7ma4603jg"; };
+  "4.04.0" = {
+    version = "unstable-20161114";
+    rev = "49c08e2e4ea8fef88692cd1dcc1b38a9133f17ac";
+    sha256 = "0ywzfkf5brj33nwh49k9if8x8v433ral25f3nbklfc9vqr06zrfl"; };
 }."${ocaml.version}";
 in
   stdenv.mkDerivation {
@@ -14,7 +18,7 @@ in
     src = fetchFromGitHub {
       owner = "alainfrisch";
       repo = "ppx_tools";
-      rev = param.version;
+      rev = if param ? rev then param.rev else param.version;
       inherit (param) sha256;
     };