diff --git a/pkgs/development/ocaml-modules/yaml/default.nix b/pkgs/development/ocaml-modules/yaml/default.nix
index 61a5a326395d..416438dafbd3 100644
--- a/pkgs/development/ocaml-modules/yaml/default.nix
+++ b/pkgs/development/ocaml-modules/yaml/default.nix
@@ -10,10 +10,11 @@ buildDunePackage rec {
 
   src = fetchurl {
     url = "https://github.com/avsm/ocaml-yaml/releases/download/v${version}/yaml-${version}.tbz";
-    sha256 = "sha256-0KngriGEpp5tcgK/43B9EEOdMacSQYYCNLGfAgRS7Mc=";
+    hash = "sha256-0KngriGEpp5tcgK/43B9EEOdMacSQYYCNLGfAgRS7Mc=";
   };
 
   minimalOCamlVersion = "4.13";
+  duneVersion = "3";
 
   buildInputs = [ dune-configurator ];
   propagatedBuildInputs = [ bos ctypes ];
diff --git a/pkgs/development/ocaml-modules/yaml/yaml-sexp.nix b/pkgs/development/ocaml-modules/yaml/yaml-sexp.nix
index d6cab9cf7f2b..aa8566ea6087 100644
--- a/pkgs/development/ocaml-modules/yaml/yaml-sexp.nix
+++ b/pkgs/development/ocaml-modules/yaml/yaml-sexp.nix
@@ -5,6 +5,8 @@ buildDunePackage rec {
 
   inherit (yaml) version src;
 
+  duneVersion = "3";
+
   propagatedBuildInputs = [ yaml ppx_sexp_conv sexplib ];
 
   meta = yaml.meta // {