diff --git a/include/tao/pq/parameter_traits_aggregate.hpp b/include/tao/pq/parameter_traits_aggregate.hpp
index f381696..034a584 100644
--- a/include/tao/pq/parameter_traits_aggregate.hpp
+++ b/include/tao/pq/parameter_traits_aggregate.hpp
@@ -27,7 +27,8 @@ namespace tao::pq
    }  // namespace internal
 
    template< typename T >
-   struct parameter_traits< T, std::enable_if_t< is_aggregate_parameter< T > > >
+      requires is_aggregate_parameter< T >
+   struct parameter_traits< T >
       : private internal::parameter_tie_aggregate< T >,
         public parameter_traits< typename internal::parameter_tie_aggregate< T >::result_t >
    {
diff --git a/include/tao/pq/result_traits.hpp b/include/tao/pq/result_traits.hpp
index d95a055..12b6b43 100644
--- a/include/tao/pq/result_traits.hpp
+++ b/include/tao/pq/result_traits.hpp
@@ -33,9 +33,6 @@ namespace tao::pq
    template< typename T >
    inline constexpr std::size_t result_traits_size< T, decltype( result_traits< T >::size ) > = result_traits< T >::size;
 
-   template< typename T >
-   concept result_traits_has_null = requires( T t ) { result_traits< T >::null(); };
-
    template<>
    struct result_traits< const char* >
    {
diff --git a/include/tao/pq/result_traits_aggregate.hpp b/include/tao/pq/result_traits_aggregate.hpp
index 2723457..b177d01 100644
--- a/include/tao/pq/result_traits_aggregate.hpp
+++ b/include/tao/pq/result_traits_aggregate.hpp
@@ -46,7 +46,8 @@ namespace tao::pq
    }  // namespace internal
 
    template< typename T >
-   struct result_traits< T, std::enable_if_t< is_aggregate_result< T > > >
+      requires is_aggregate_result< T >
+   struct result_traits< T >
       : internal::aggregate_result< T >
    {};
 
diff --git a/include/tao/pq/result_traits_array.hpp b/include/tao/pq/result_traits_array.hpp
index 34aa4d9..80603d1 100644
--- a/include/tao/pq/result_traits_array.hpp
+++ b/include/tao/pq/result_traits_array.hpp
@@ -82,7 +82,7 @@ namespace tao::pq
                if( const auto* end = std::strpbrk( value, ",;}" ) ) {
                   std::string input( value, end );
                   if( input == "NULL" ) {
-                     if constexpr( result_traits_has_null< value_type > ) {
+                     if constexpr( requires { result_traits< value_type >::null(); } ) {
                         container.push_back( result_traits< value_type >::null() );
                      }
                      else {
@@ -124,7 +124,8 @@ namespace tao::pq
    }  // namespace internal
 
    template< typename T >
-   struct result_traits< T, std::enable_if_t< is_array_result< T > > >
+      requires is_array_result< T >
+   struct result_traits< T >
    {
       static auto from( const char* value ) -> T
       {
diff --git a/include/tao/pq/result_traits_tuple.hpp b/include/tao/pq/result_traits_tuple.hpp
index 94b7e81..eb930d7 100644
--- a/include/tao/pq/result_traits_tuple.hpp
+++ b/include/tao/pq/result_traits_tuple.hpp
@@ -18,8 +18,9 @@ struct tao::pq::result_traits< std::tuple< T > >
    static constexpr std::size_t size = result_traits_size< T >;
 
    template< typename U = T >
+      requires std::is_same_v< T, U > && requires { result_traits< T >::null(); }
    [[nodiscard]] static auto null()
-      -> std::enable_if_t< std::is_same_v< T, U > && result_traits_has_null< T >, std::tuple< T > >
+      -> std::tuple< T >
    {
       return std::tuple< T >( result_traits< T >::null() );
    }
diff --git a/include/tao/pq/row.hpp b/include/tao/pq/row.hpp
index f30dfb2..d8b3840 100644
--- a/include/tao/pq/row.hpp
+++ b/include/tao/pq/row.hpp
@@ -221,7 +221,7 @@ namespace tao::pq
             TAO_PQ_UNREACHABLE;  // LCOV_EXCL_LINE
          }
          else if constexpr( ( result_traits_size< T > == 1 ) && !is_aggregate_result< T > ) {
-            if constexpr( result_traits_has_null< T > ) {
+            if constexpr( requires { result_traits< T >::null(); } ) {
                if( is_null( column ) ) {
                   return result_traits< T >::null();
                }
diff --git a/include/tao/pq/table_row.hpp b/include/tao/pq/table_row.hpp
index d34b104..10883ab 100644
--- a/include/tao/pq/table_row.hpp
+++ b/include/tao/pq/table_row.hpp
@@ -213,7 +213,7 @@ namespace tao::pq
          else if constexpr( result_traits_size< T > == 1 ) {
             const char* const value = get( column );
             if( value == nullptr ) {
-               if constexpr( result_traits_has_null< T > ) {
+               if constexpr( requires { result_traits< T >::null(); } ) {
                   return result_traits< T >::null();
                }
                else {