Can't reorder feature in tree (throwing XToolkitBadContext)

Hi, I'm desperate,

I'm trying to reorder feature in tree after last feature.

Both features are completely independent. My code:

Feature sketch = ...
Feature last = ...
ReorderAfterOperation op = sketch.CreateReorderAfterOp(last);
FeatureOperations ops = FeatureOperations.create();
ops.append(op);
model.ExecuteFeatureOps(ops, null); --> throws XToolkitBadContext exception

Any ideas ?

Thanks.