Failing on PyPY, even though I set skip?

I"ve got a pacakge with a C python extension that is failing on PyPy – which does not surprise me. But I set it to skip PyPy – so why is it trying?

build:
  number: 1007
  script: "{{ PYTHON }} -m pip install . -vv"
  skip: True  # [py<39 or python_impl == 'pypy']

what am I missing?