diff --git a/frontend/exporter/src/types/copied.rs b/frontend/exporter/src/types/copied.rs
index 2fcb8f874..69944cd61 100644
--- a/frontend/exporter/src/types/copied.rs
+++ b/frontend/exporter/src/types/copied.rs
@@ -225,7 +225,7 @@ impl<'tcx, S: UnderOwnerState<'tcx>> SInto<S, ConstantExpr> for rustc_middle::mi
     fn sinto(&self, s: &S) -> ConstantExpr {
         use rustc_middle::mir::Const;
         let tcx = s.base().tcx;
-        match self.eval_constant(s).as_ref().unwrap_or(self) {
+        match self {
             Const::Val(const_value, ty) => const_value_to_constant_expr(
                 s,
                 ty.clone(),
@@ -239,7 +239,11 @@ impl<'tcx, S: UnderOwnerState<'tcx>> SInto<S, ConstantExpr> for rustc_middle::mi
                     .def_ident_span(ucv.def)
                     .unwrap_or_else(|| ucv.def.default_span(tcx));
                 if let Some(_) = ucv.promoted {
-                    supposely_unreachable_fatal!(s[span], "PromotedConstant"; {ucv.def})
+                    self.eval_constant(s)
+                        .unwrap_or_else(|| {
+                            supposely_unreachable_fatal!(s, "UnevalPromotedConstant"; {self, ucv});
+                        })
+                        .sinto(s)
                 } else {
                     match self.translate_uneval(s, ucv.shrink(), span) {
                         TranslateUnevalRes::EvaluatedConstant(c) => c.sinto(s),