diff --git a/pkgs/development/python-modules/pyefergy/default.nix b/pkgs/development/python-modules/pyefergy/default.nix
index 7b7e587feddb..87f2abda0c0b 100644
--- a/pkgs/development/python-modules/pyefergy/default.nix
+++ b/pkgs/development/python-modules/pyefergy/default.nix
@@ -22,6 +22,12 @@ buildPythonPackage rec {
     hash = "sha256-AdoM+PcVoajxhnEfkyN9UuNufChu8XGmZDLNC3mjrps=";
   };
 
+  postPatch = ''
+    # setuptools.extern.packaging.version.InvalidVersion: Invalid version: 'master'
+    substituteInPlace setup.py \
+      --replace 'version="master",' 'version="${version}",'
+  '';
+
   propagatedBuildInputs = [
     aiohttp
     iso4217