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 \