There is no such breakage at all, the assumption that casing and collation can happen without locale-specific information is invalid, Unicode isn't designed to

There is no such breakage at all, the assumption that casing and collation can happen without locale-specific information is invalid, Unicode isn't designed to prevent this and we'd hate it if it was. This may not be a solved problem in a given programming language's standard library, and/or one might see a bug such as the one GP was reporting, but neither of these conditions is inevitable, here's how you do it in Swift: "i".uppercased(with: Locale(identifier: "tr_TR")) // returns "İ" "i".uppercased(with: Locale(identifier: "en_US")) // returns "I" Same deal with "ij".uppercased and "nl_NL" locale. It's not a bug that Unicode just threw its hands up and said that complex string operations are locale-specific. The more you learn about the various scripts it represents, the more you will appreciate that there is no other choice.