diff --git a/src/core/include/mp-units/unit.h b/src/core/include/mp-units/unit.h
index a15b0f7c..c4343c45 100644
--- a/src/core/include/mp-units/unit.h
+++ b/src/core/include/mp-units/unit.h
@@ -695,7 +695,7 @@ constexpr Out print_separator(Out out, unit_symbol_formatting fmt)
 template<Unit U>
 [[nodiscard]] consteval bool has_unit_symbol(U)
 {
-  return !std::derived_from<U, derived_unit<>>;
+  return requires { U::symbol; } || !std::derived_from<U, derived_unit<>>;
 }
 
 template<typename CharT, std::output_iterator<CharT> Out, Unit U>