diff --git a/pkgs/development/ocaml-modules/zarith/default.nix b/pkgs/development/ocaml-modules/zarith/default.nix
index 10ac88bcb90b..2f679da977d7 100644
--- a/pkgs/development/ocaml-modules/zarith/default.nix
+++ b/pkgs/development/ocaml-modules/zarith/default.nix
@@ -3,13 +3,16 @@
 let
   ocaml_version = (builtins.parseDrvName ocaml.name).version;
 in
+
+assert stdenv.lib.versionAtLeast ocaml_version "3.12.1";
+
 stdenv.mkDerivation rec {
   name = "zarith-${version}";
-  version = "1.2.1";
+  version = "1.3";
 
   src = fetchurl {
-    url = "http://forge.ocamlcore.org/frs/download.php/1199/${name}.tgz";
-    sha256 = "0i21bsx41br0jgw8xmlpnky5zamzqkpbykrq0z53z7ar77602s4i";
+    url = http://forge.ocamlcore.org/frs/download.php/1471/zarith-1.3.tgz;
+    sha256 = "1mx3nxcn5h33qhx4gbg0hgvvydwlwdvdhqcnvfwnmf9jy3b8frll";
   };
 
   buildInputs = [ ocaml findlib pkgconfig gmp perl ];
@@ -22,11 +25,11 @@ stdenv.mkDerivation rec {
   '';
   preInstall = "mkdir -p $out/lib/ocaml/${ocaml_version}/site-lib";
 
-  meta = {
+  meta = with stdenv.lib; {
     description = "fast, arbitrary precision OCaml integers";
     homepage    = "http://forge.ocamlcore.org/projects/zarith";
-    license     = stdenv.lib.licenses.lgpl2;
+    license     = licenses.lgpl2;
     platforms   = ocaml.meta.platforms;
-    maintainers = [ stdenv.lib.maintainers.thoughtpolice ];
+    maintainers = with maintainers; [ thoughtpolice vbgl ];
   };
 }