It appears that our other checker (Chatter) accepts this. So, it is just a problem with CHECK. I will see if Leonid can remove this constraint in CHECK. By the way, doesn't this remind you of the subject of:
Menn, L., & MacWhinney, B. (1984). The repeated morph constraint: Toward an explanation. Language, 19, 519-541.
I always wanted the title of that article to be "Enough is enough". So why do we have to write &=squeals nine times?
-- Brian MacWhinney, Teresa Heinz Professor of Cognitive Psychology, LTI and Modern Languages, CMU