diff --git a/compiler/rustc_borrowck/src/type_check/input_output.rs b/compiler/rustc_borrowck/src/type_check/input_output.rs
index 17e702eb8c528..7a35cb97ede87 100644
--- a/compiler/rustc_borrowck/src/type_check/input_output.rs
+++ b/compiler/rustc_borrowck/src/type_check/input_output.rs
@@ -151,7 +151,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             // `rustc_traits::normalize_after_erasing_regions`. Ideally, we'd
             // like to normalize *before* inserting into `local_decls`, but
             // doing so ends up causing some other trouble.
-            let b = self.normalize(b, Locations::All(span));
+            let _b = self.normalize(b, Locations::All(span));
 
             // Note: if we have to introduce new placeholders during normalization above, then we won't have
             // added those universes to the universe info, which we would want in `relate_tys`.