diff --git a/src/core/include/mp-units/bits/quantity_cast.h b/src/core/include/mp-units/bits/quantity_cast.h
index a78bac95e..65d51c2d9 100644
--- a/src/core/include/mp-units/bits/quantity_cast.h
+++ b/src/core/include/mp-units/bits/quantity_cast.h
@@ -51,9 +51,9 @@ template<QuantitySpec auto ToQS, typename Q>
 {
   if constexpr (detail::QuantityKindSpec<std::remove_const_t<decltype(ToQS)>> &&
                 AssociatedUnit<std::remove_const_t<decltype(Q::unit)>>)
-    return make_quantity<q.unit>(std::forward<Q>(q).value());
+    return make_quantity<Q::unit>(std::forward<Q>(q).value());
   else
-    return make_quantity<reference<ToQS, q.unit>{}>(std::forward<Q>(q).value());
+    return make_quantity<reference<ToQS, Q::unit>{}>(std::forward<Q>(q).value());
 }
 
 }  // namespace mp_units