How can I import a multi-select quiz question to be scored by Correct Selections?

I am importing quiz questions into the Question Library using csv files, but the import syntax doesn't seem to be working as expected. When I specify "Correct Selections" as the scoring method, as described in the documentation, the questions still import with All or Nothing scoring. I've tried both "Correct Selections" and "CorrectSelections" (without the space—the fact that the table in the documentation specifies "RightMinusWrong" (no spaces) but "Correct Selections" (with a space) seems odd to me), but the result is the same. Any suggestions on how to fix this?