diff --git a/pkgs/development/python-modules/fn/default.nix b/pkgs/development/python-modules/fn/default.nix
index f64d1a3d122d..0acdf24d9542 100644
--- a/pkgs/development/python-modules/fn/default.nix
+++ b/pkgs/development/python-modules/fn/default.nix
@@ -1,20 +1,34 @@
-{ lib, buildPythonPackage, fetchPypi }:
+{ lib
+, buildPythonPackage
+, fetchpatch
+, fetchPypi
+}:
 
 buildPythonPackage rec {
   pname = "fn";
   version = "0.4.3";
 
-  meta = {
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "1nmsjmn8jb4gp22ksx0j0hhdf4y0zm8rjykyy2i6flzimg6q1kgq";
+  };
+
+  patches = [
+    (fetchpatch {
+      url = "https://github.com/kachayev/fn.py/commit/a54fc0bd8aeae277de2db726131d249ce607c0c2.patch";
+      hash = "sha256-I0ZISOgVibsc1k7gwSfeW6qV9PspQqdaHlRLr/IusQ8=";
+      excludes = [
+        "fn/monad.py"
+      ];
+    })
+  ];
+
+  meta = with lib; {
     description = ''
       Functional programming in Python: implementation of missing
       features to enjoy FP
     '';
     homepage = "https://github.com/kachayev/fn.py";
-    license = lib.licenses.asl20;
-  };
-
-  src = fetchPypi {
-    inherit pname version;
-    sha256 = "1nmsjmn8jb4gp22ksx0j0hhdf4y0zm8rjykyy2i6flzimg6q1kgq";
+    license = licenses.asl20;
   };
 }