diff --git a/include/xo/randomgen/distribution_concept.hpp b/include/xo/randomgen/distribution_concept.hpp
index 61c764e0..c2343255 100644
--- a/include/xo/randomgen/distribution_concept.hpp
+++ b/include/xo/randomgen/distribution_concept.hpp
@@ -24,12 +24,17 @@ namespace xo {
             // os << dist
             // is >> dist
 
-        } && std::copyable<Distribution>
+        }
+#ifdef __clang__
+        // std::copyable apparently not available in clang11 ?
+#else
+        && std::copyable<Distribution>
         && std::copyable<typename Distribution::param_type>
-        && std::equality_comparable<typename Distribution::param_type>;
+        && std::equality_comparable<typename Distribution::param_type>
+#endif
+        ;
     } /*namespace rng*/
 
 } /*namespace xo*/
 
-
 /* end distribution_concept.hpp */
diff --git a/include/xo/randomgen/engine_concept.hpp b/include/xo/randomgen/engine_concept.hpp
index 38b65cd7..2b3a2e53 100644
--- a/include/xo/randomgen/engine_concept.hpp
+++ b/include/xo/randomgen/engine_concept.hpp
@@ -7,6 +7,8 @@
 
 namespace std {
 #ifdef __clang__
+
+# if __clang_major__ <= 11
     template < class T >
     concept integral = std::is_integral_v<T>;
 
@@ -31,8 +33,11 @@ namespace std {
         && requires { { G::min() } -> std::same_as<std::invoke_result_t<G&>>;
                       { G::max() } -> std::same_as<std::invoke_result_t<G&>>;
                       requires std::bool_constant<(G::min() < G::max())>::value; };
+# endif
+
 #else
     /* uniform_random_bit_generator provided by gcc 12.3.2 */
+    /* uniform_random_bit_generator provided by clang 16 */
 #endif
 } /*namespace std*/