diff --git a/src/core/include/mp-units/framework/quantity_spec_concepts.h b/src/core/include/mp-units/framework/quantity_spec_concepts.h
index d801a7f9..e7d4745f 100644
--- a/src/core/include/mp-units/framework/quantity_spec_concepts.h
+++ b/src/core/include/mp-units/framework/quantity_spec_concepts.h
@@ -53,7 +53,7 @@ struct kind_of_;
 namespace detail {
 
 template<typename T>
-concept QuantityKindSpec = is_specialization_of<T, kind_of_>;
+concept QuantityKindSpec = QuantitySpec<T> && is_specialization_of<T, kind_of_>;
 
 #if MP_UNITS_API_NO_CRTP
 template<auto... Args>