diff --git a/pkgs/applications/misc/buku/default.nix b/pkgs/applications/misc/buku/default.nix
index 60ade661cff..5db3e7d0c8c 100644
--- a/pkgs/applications/misc/buku/default.nix
+++ b/pkgs/applications/misc/buku/default.nix
@@ -54,6 +54,8 @@ with python3.pkgs; buildPythonApplication rec {
       --replace "@pytest.mark.slowtest" "@unittest.skip('skipping')" \
       --replace "self.assertEqual(shorturl, 'http://tny.im/yt')" "" \
       --replace "self.assertEqual(url, 'https://www.google.com')" ""
+    substituteInPlace setup.py \
+      --replace mypy-extensions==0.4.1 mypy-extensions>=0.4.1
   '';
 
   postInstall = ''