diff --git a/pkgs/python-packages/pyln-proto/default.nix b/pkgs/python-packages/pyln-proto/default.nix
index cde5e44..98f7d6b 100644
--- a/pkgs/python-packages/pyln-proto/default.nix
+++ b/pkgs/python-packages/pyln-proto/default.nix
@@ -29,4 +29,9 @@ buildPythonPackage rec {
   checkInputs = [ pytestCheckHook ];
 
   postUnpack = "sourceRoot=$sourceRoot/contrib/pyln-proto";
+
+  postPatch = ''
+    substituteInPlace pyproject.toml \
+      --replace-fail 'cryptography = "^42"' 'cryptography = "43.0.1"'
+  '';
 }