diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 98e93ad3fc50..bcdfa4f12d35 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -834,7 +834,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                                     let reported =
                                         tcx.sess.emit_err(UnableToConstructConstantValue {
                                             span: tcx.def_span(def_id),
-                                            unevaluated,
+                                            unevaluated: unevaluated.expand(),
                                         });
                                     Err(ErrorHandled::Reported(reported))
                                 }