Compilation fail using Rust nightly: The attribute export_macro is currently unknown to the compiler and may have meaning added to it in the future

[oherrala]

Using Rust nightly: rustc 1.17.0-nightly (824c9ebbd 2017-03-12)

and compiling rustls as dependency to my crate I get:

error: The attribute `export_macro` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
 --> /Users/oherrala/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.5.7/src/msgs/macros.rs:3:1
  |
3 | #[export_macro]
  | ^^^^^^^^^^^^^^^
  |
  = help: add #![feature(custom_attribute)] to the crate attributes to enable

error: aborting due to previous error

Rust issue: rust-lang/rust#29642