diff --git a/library/proc_macro/src/bridge/mod.rs b/library/proc_macro/src/bridge/mod.rs
index 03c3e697cfe..52cc8fba043 100644
--- a/library/proc_macro/src/bridge/mod.rs
+++ b/library/proc_macro/src/bridge/mod.rs
@@ -7,6 +7,10 @@
 //! Rust ABIs (e.g., stage0/bin/rustc vs stage1/bin/rustc during bootstrap).
 
 #![deny(unsafe_code)]
+// proc_macros anyway don't work on wasm hosts so while both sides of this bridge can
+// be built with different versions of rustc, the wasm ABI changes don't really matter.
+#![cfg_attr(bootstrap, allow(unknown_lints))]
+#![allow(wasm_c_abi)]
 
 use std::hash::Hash;
 use std::ops::{Bound, Range};