ca8b75466ce seems to be responsible; using the `backtrace` module even when the feature is disabled and that module is not compiled. These two lines in particular cause errors: https://github.com/rust-lang/rust/commit/ca8b75466cef854d30fdf7614c2358b1eb46816e#diff-bf0874963583c8c7f5645b5e6ea0e5e7R57 https://github.com/rust-lang/rust/commit/ca8b75466cef854d30fdf7614c2358b1eb46816e#diff-c31566eec0e481d86864fc4152b3df33R362