diff --git a/artiq/firmware/libdrtioaux/lib.rs b/artiq/firmware/libdrtioaux/lib.rs
index 6daa6f802..4cdf0416c 100644
--- a/artiq/firmware/libdrtioaux/lib.rs
+++ b/artiq/firmware/libdrtioaux/lib.rs
@@ -8,9 +8,11 @@ extern crate board;
 extern crate byteorder;
 
 mod proto;
+#[cfg(has_drtio)]
 mod crc32;
 
 use std::io::{self, Read, Write};
+#[cfg(has_drtio)]
 use core::slice;
 use proto::*;