diff --git a/pkgs/development/python-modules/nox/default.nix b/pkgs/development/python-modules/nox/default.nix
index 2751d971c175d..9485022155da8 100644
--- a/pkgs/development/python-modules/nox/default.nix
+++ b/pkgs/development/python-modules/nox/default.nix
@@ -29,6 +29,11 @@ buildPythonPackage rec {
     hash = "sha256-GdNz34A8IKwPG/270sY5t3SoggGCZMWfDq/Wyhk0ez8=";
   };
 
+  patches = [
+    # Backport of https://github.com/wntrblm/nox/pull/903, which can be removed on next release
+    ./fix-broken-mock-on-cpython-3.12.8.patch
+  ];
+
   build-system = [ hatchling ];
 
   dependencies =
diff --git a/pkgs/development/python-modules/nox/fix-broken-mock-on-cpython-3.12.8.patch b/pkgs/development/python-modules/nox/fix-broken-mock-on-cpython-3.12.8.patch
new file mode 100644
index 0000000000000..f634c3534b93a
--- /dev/null
+++ b/pkgs/development/python-modules/nox/fix-broken-mock-on-cpython-3.12.8.patch
@@ -0,0 +1,35 @@
+diff --git a/nox/command.py b/nox/command.py
+index 671875c..4984168 100644
+--- a/nox/command.py
++++ b/nox/command.py
+@@ -30,6 +30,8 @@ TYPE_CHECKING = False
+ if TYPE_CHECKING:
+     from typing import IO
+ 
++_PLATFORM = sys.platform
++
+ ExternalType = Literal["error", True, False]
+ 
+ 
+@@ -63,7 +65,7 @@ def _clean_env(env: Mapping[str, str | None] | None = None) -> dict[str, str] |
+     clean_env = {k: v for k, v in env.items() if v is not None}
+ 
+     # Ensure systemroot is passed down, otherwise Windows will explode.
+-    if sys.platform == "win32":
++    if _PLATFORM.startswith("win"):
+         clean_env.setdefault("SYSTEMROOT", os.environ.get("SYSTEMROOT", ""))
+ 
+     return clean_env
+diff --git a/tests/test_command.py b/tests/test_command.py
+index ae398e9..904cf34 100644
+--- a/tests/test_command.py
++++ b/tests/test_command.py
+@@ -157,7 +157,7 @@ def test_run_env_remove(monkeypatch):
+     )
+ 
+ 
+-@mock.patch("sys.platform", "win32")
++@mock.patch("nox.command._PLATFORM", "win32")
+ def test_run_env_systemroot():
+     systemroot = os.environ.setdefault("SYSTEMROOT", "sigil")
+