URGENT MAJOR BUG!! xxx_does_not_equal(array) doesn't work properly

[jaycode]

possible_variants.sku_equals(array_of_sku)

returns:

SELECT * FROM variants WHERE ((variants.sku IN ('DUVR14FL-BS-T','DUVR14FL-BS-K')) AND (variants.product_id = 2))

but possible_variants.sku_does_not_equal(array_of_sku)

returns:

SELECT * FROM variants WHERE ((variants.sku != 'DUVR14FL-BS-T','DUVR14FL-BS-K') AND (variants.product_id = 1))

Thus giving error message:

Mysql::Error: Operand should contain 1 column(s):