diff --git a/pkgs/development/python-modules/gentools/default.nix b/pkgs/development/python-modules/gentools/default.nix
index d3f45cdea7f0..c53dd68fb815 100644
--- a/pkgs/development/python-modules/gentools/default.nix
+++ b/pkgs/development/python-modules/gentools/default.nix
@@ -4,14 +4,14 @@
 
 buildPythonPackage rec {
   pname = "gentools";
-  version = "1.1.0";
+  version = "1.2.1";
 
   # Pypi doesn't ship the tests, so we fetch directly from GitHub
   src = fetchFromGitHub {
     owner = "ariebovenberg";
     repo = pname;
-    rev = "v${version}";
-    sha256 = "1sm6cqi7fv2k3pc68r7wvvjjz8y6cjmz8bvxgqfa4v4wxibwnwrl";
+    rev = "refs/tags/v${version}";
+    sha256 = "sha256-RBUIji3FOIRjfp4t7zBAVSeiWaYufz4ID8nTWmhDkf8=";
   };
 
   propagatedBuildInputs =