Sorry - I try hard to avoid this situation, but sometimes something slips through the cracks. The source I use for these quizzes compiles words that are valid across all Scrabble dictionaries. Gilet is valid in some but not others, just as ribbit was in Saturday Stumper #1. Fortunately in this case it's not far to go from g to f :)
I updated the caveats to include a note about words being valid across all Scrabble dictionaries. For some reason 'gilet' (nor 'polony', as someone else pointed out) isn't.
I had to just run through the alphabet to get "filet".
What's ligma?