diff --git a/src/include/units/quantity.h b/src/include/units/quantity.h
index 34d3ac45..0aad7ff3 100644
--- a/src/include/units/quantity.h
+++ b/src/include/units/quantity.h
@@ -96,7 +96,7 @@ namespace units {
   }  // namespace detail
 
   template<Quantity To, Dimension D, Unit U, Number Rep>
-      requires std::experimental::ranges::Same<typename To::dimension, D> constexpr
+      requires std::experimental::ranges::Same<typename To::dimension, D>
   constexpr To quantity_cast(const quantity<D, U, Rep>& q)
   {
     using c_ratio = std::ratio_divide<typename U::ratio, typename To::unit::ratio>;