diff --git a/build123d/default.nix b/build123d/default.nix
index 6c9cdfc..035045f 100644
--- a/build123d/default.nix
+++ b/build123d/default.nix
@@ -107,6 +107,10 @@
               packages = [
                 pyEnv
               ];
+
+              shellHook = ''
+                export PYTHONPATH="${pyEnv}/${pyEnv.sitePackages}:$PYTHONPATH"
+              '';
             }
             // cfg.devShell.extraAttrs);
 
diff --git a/build123d/template/build3d.py b/build123d/template/build3d.py
index edcb619..6c2cbb0 100644
--- a/build123d/template/build3d.py
+++ b/build123d/template/build3d.py
@@ -1,8 +1,10 @@
-from build123d import *  # pyright: ignore[reportWildcardImportFromLibrary]
+# pyright: reportUnusedCallResult=false, reportWildcardImportFromLibrary=false
+from build123d import *
 
 length, width, thickness = 80.0, 60.0, 10.0
 
 with BuildPart() as builder:
     Box(length, width, thickness)
 
+assert builder.part is not None
 export_step(builder.part, "output.step")