diff --git a/pkgs/by-name/ac/acgtk/package.nix b/pkgs/by-name/ac/acgtk/package.nix
index 420f53ef35d6..599e2f522002 100644
--- a/pkgs/by-name/ac/acgtk/package.nix
+++ b/pkgs/by-name/ac/acgtk/package.nix
@@ -2,6 +2,7 @@
   lib,
   stdenv,
   fetchFromGitLab,
+  fetchpatch,
   ocamlPackages,
 }:
 
@@ -18,6 +19,14 @@ stdenv.mkDerivation {
     hash = "sha256-XuPcubt1lvnQio+km6MhmDu41NXNVXKKpzGd/Y1XzLo=";
   };
 
+  # Compatibility with fmt 0.10.0
+  patches = [
+    (fetchpatch {
+      url = "https://gitlab.inria.fr/ACG/dev/ACGtk/-/commit/613454b376d10974f539ab398a269be061c5bc9c.patch";
+      hash = "sha256-l/V8oEgntnFtrhpTQSk7PkpaX+dBq4izG/tloCQRbDY=";
+    })
+  ];
+
   # Compatibility with logs 0.8.0
   postPatch = ''
     substituteInPlace src/utils/dune \
diff --git a/pkgs/development/ocaml-modules/fmt/default.nix b/pkgs/development/ocaml-modules/fmt/default.nix
index bd86aa8f68b9..b46f9acd8800 100644
--- a/pkgs/development/ocaml-modules/fmt/default.nix
+++ b/pkgs/development/ocaml-modules/fmt/default.nix
@@ -14,12 +14,12 @@ if lib.versionOlder ocaml.version "4.08" then
 else
 
   stdenv.mkDerivation rec {
-    version = "0.9.0";
+    version = "0.10.0";
     pname = "ocaml${ocaml.version}-fmt";
 
     src = fetchurl {
       url = "https://erratique.ch/software/fmt/releases/fmt-${version}.tbz";
-      sha256 = "sha256-8fsggFoi3XWhN9cnBKNw53ic9r32OUjmgX0cImwUEmE=";
+      sha256 = "sha256-eDgec+FW2F85LzfkKFqsmYd3MWWZsBIXMhlXT3xdKZc=";
     };
 
     nativeBuildInputs = [