In an attribute selector eg [href^="https://"i] is whitespace required before the i?

[CecilSWard]

See https://stackoverflow.com/questions/79668759/is-whitespace-required-between-the-attribute-selector-sensitivty-flag-and-a-prec

The CSS validator seems to think that whitespace is required before the case-sensitivity flag (‘s’ or ‘i’) a raises an error if no space is present. The above-mentioned post says that whitespace here is optional.

[CecilSWard]

Is this a bug in the CSS validator? Tested in Safari and Firefox on iPad, the no-space CSS seems to work fine, as expected. As far as I can see, the examples given all have whitespace before the ‘i’.