diff --git a/pkgs/development/ocaml-modules/bwd/default.nix b/pkgs/development/ocaml-modules/bwd/default.nix
index aa762502a59..bff1de9bc86 100644
--- a/pkgs/development/ocaml-modules/bwd/default.nix
+++ b/pkgs/development/ocaml-modules/bwd/default.nix
@@ -2,15 +2,16 @@
 
 buildDunePackage rec {
   pname = "bwd";
-  version = "2.0.0";
+  version = "2.1.0";
 
   minimalOCamlVersion = "4.12";
+  duneVersion = "3";
 
   src = fetchFromGitHub {
     owner = "RedPRL";
     repo = "ocaml-bwd";
     rev = version;
-    sha256 = "sha256:0zgi8an53z6wr6nzz0zlmhx19zhqy1w2vfy1sq3sikjwh74jjq60";
+    hash = "sha256-ucXOBjD1behL2h8CZv64xtRjCPkajZic7G1oxxDmEXY=";
   };
 
   doCheck = true;
diff --git a/pkgs/development/ocaml-modules/cooltt/default.nix b/pkgs/development/ocaml-modules/cooltt/default.nix
index 837a06a2fde..b19e01ceb34 100644
--- a/pkgs/development/ocaml-modules/cooltt/default.nix
+++ b/pkgs/development/ocaml-modules/cooltt/default.nix
@@ -49,6 +49,8 @@ let
       sha256 = "sha256:1xb754fha4s0bgjfqjxzqljvalmkfdwdn5y4ycsp51wiah235bsy";
     };
 
+    duneVersion = "3";
+
     propagatedBuildInputs = [ bwd ];
 
     doCheck = true;