If a bug has been shipped to production and people are depending on it, it isn't a bug but a feature. If you then "fix" it without notice, it is a breaking change. This is all software/platform development 101.
Sounds like the issue is they corrected the bug without documenting the breaking change and did it with minimal notice. Worse yet is that the API change will impact all software running on the host. So even if your distributed program works today, it will subtlety break when the user upgrades their host OS.
