diff --git a/pkgs/development/ocaml-modules/json-data-encoding/bson.nix b/pkgs/development/ocaml-modules/json-data-encoding/bson.nix
index 46810ab1566..c0d1a5260bc 100644
--- a/pkgs/development/ocaml-modules/json-data-encoding/bson.nix
+++ b/pkgs/development/ocaml-modules/json-data-encoding/bson.nix
@@ -5,6 +5,8 @@ buildDunePackage {
 
   inherit (json-data-encoding) version src doCheck;
 
+  duneVersion = "3";
+
   propagatedBuildInputs = [
     json-data-encoding
     ocplib-endian
diff --git a/pkgs/development/ocaml-modules/json-data-encoding/default.nix b/pkgs/development/ocaml-modules/json-data-encoding/default.nix
index 13b81d9c527..ef89f7a205b 100644
--- a/pkgs/development/ocaml-modules/json-data-encoding/default.nix
+++ b/pkgs/development/ocaml-modules/json-data-encoding/default.nix
@@ -2,13 +2,14 @@
 
 buildDunePackage rec {
   pname = "json-data-encoding";
-  version = "0.11";
+  version = "0.12.1";
   minimalOCamlVersion = "4.10";
+  duneVersion = "3";
   src = fetchFromGitLab {
     owner = "nomadic-labs";
     repo = "json-data-encoding";
     rev = "${version}";
-    sha256 = "sha256-4FNUU82sq3ylgw0lxHlwi1OV58NRRh9zJqE47YyQZSc=";
+    hash = "sha256-ticulOKiFNQIZNFOQE9UQOw/wqRfygQwLVIc4kkmwg4=";
   };
 
   propagatedBuildInputs = [