Very strange (to me) problem

Hello,

I'm working through a python tutorial on natural language processing. There is a code sample using a for loop, thus:

my_stop_words = ['say', 'be', 'said', 'says', 'saying', 'field']
for stopword in my_stop_words:
    lexeme = nlp.vocab[stopword]
    lexeme.is_stop = True

in Linux, PyCharm complains that there is a typo in "stopword".

In Windows it does not complain.

Can anyone explain what is going on here. I'm confused and too much of a novice to be able to figure it out.

Thank you