diff --git a/pkgs/development/python-modules/assay/default.nix b/pkgs/development/python-modules/assay/default.nix
index 468e3254a4519..d4cdd4d04cf53 100644
--- a/pkgs/development/python-modules/assay/default.nix
+++ b/pkgs/development/python-modules/assay/default.nix
@@ -3,12 +3,13 @@
   buildPythonPackage,
   fetchFromGitHub,
   pythonAtLeast,
+  setuptools,
 }:
 
 buildPythonPackage {
   pname = "assay";
   version = "0-unstable-2024-05-09";
-  format = "setuptools";
+  pyproject = true;
 
   src = fetchFromGitHub {
     owner = "brandon-rhodes";
@@ -17,6 +18,13 @@ buildPythonPackage {
     hash = "sha256-zYpLtcXZ16EJWKSCqxFkSz/G9PwIZEQGBrYiJKuqnc4=";
   };
 
+  build-system = [ setuptools ];
+
+  postPatch = lib.optionalString (pythonAtLeast "3.14") ''
+    substituteInPlace assay/assertion.py \
+      --replace-fail "op.load_assertion_error" "op.load_common_constant"
+  '';
+
   pythonImportsCheck = [ "assay" ];
 
   meta = {
diff --git a/pkgs/development/python-modules/skyfield/default.nix b/pkgs/development/python-modules/skyfield/default.nix
index ad25d62fc9bae..941829ea87340 100644
--- a/pkgs/development/python-modules/skyfield/default.nix
+++ b/pkgs/development/python-modules/skyfield/default.nix
@@ -1,7 +1,6 @@
 {
   lib,
   buildPythonPackage,
-  pythonOlder,
   fetchFromGitHub,
   setuptools,
   certifi,
@@ -16,14 +15,14 @@
 
 buildPythonPackage rec {
   pname = "skyfield";
-  version = "1.53";
+  version = "1.54";
   pyproject = true;
 
   src = fetchFromGitHub {
     owner = "skyfielders";
     repo = "python-skyfield";
     rev = version;
-    hash = "sha256-CQe+ik6HciOUaRpFp8Cx6cOlOFzeVoMVJrk7+rdcQEo=";
+    hash = "sha256-oZEmc8BVqs3eSaqrjyR/wQu1WTLv4A0a/dpEZduCXqk=";
   };
 
   # Fix broken tests on "exotic" platforms.