diff --git a/artiq/firmware/libproto_artiq/lib.rs b/artiq/firmware/libproto_artiq/lib.rs
index 66c04d5e6..e26ddf1e0 100644
--- a/artiq/firmware/libproto_artiq/lib.rs
+++ b/artiq/firmware/libproto_artiq/lib.rs
@@ -1,5 +1,6 @@
 #![no_std]
 #![cfg_attr(feature = "alloc", feature(alloc))]
+#![feature(extern_prelude)]
 
 extern crate failure;
 #[macro_use]