diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index eaef4c7b54a..995034e81da 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -8,3 +8,7 @@
 
 pub mod bit_set;
 pub mod vec;
+
+// FIXME(#56935): Work around ICEs during cross-compilation.
+#[allow(unused)]
+extern crate rustc_macros;