diff --git a/pkgs/applications/science/math/pynac/default.nix b/pkgs/applications/science/math/pynac/default.nix
index 87fb205174bf..e3474d865e2d 100644
--- a/pkgs/applications/science/math/pynac/default.nix
+++ b/pkgs/applications/science/math/pynac/default.nix
@@ -1,5 +1,6 @@
 { stdenv
 , fetchFromGitHub
+, fetchurl
 , autoreconfHook
 , pkgconfig
 , flint
@@ -33,6 +34,14 @@ stdenv.mkDerivation rec {
     pkgconfig
   ];
 
+  patches = [
+    (fetchurl {
+      name = "py_ssize_t_clean.patch";
+      url = "https://git.sagemath.org/sage.git/plain/build/pkgs/pynac/patches/py_ssize_t_clean.patch?h=9.2";
+      sha256 = "0l3gbg9hc4v671zf4w376krnk3wh8hj3649610nlvzzxckcryzab";
+    })
+  ];
+
   meta = with stdenv.lib; {
     description = "Python is Not a CAS -- modified version of Ginac";
     longDescription = ''