diff --git a/pyproject.toml b/pyproject.toml
index 7895991a4e..28b39ba457 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -250,6 +250,7 @@ cmake-format = "gersemi . --in-place"
 # --ignore unresolved-reference: walrus operator false positives in ty.
 cmd = """
     ty check
+    nix/
     src/bcf
     src/bsdd
     src/ifc2ca