diff --git a/test/common_type_4_test.cpp b/test/common_type_4_test.cpp
index d046b6a..efbb172 100644
--- a/test/common_type_4_test.cpp
+++ b/test/common_type_4_test.cpp
@@ -51,7 +51,10 @@ TT_TEST_BEGIN(common_type_4)
 
     BOOST_CHECK_TYPE(tt::common_type<UDT()>::type, UDT(*)());
     BOOST_CHECK_TYPE(tt::common_type<UDT const()>::type, UDT const(*)());
+#if __cplusplus <= 201703
+    // Deprecated in C++20:
     BOOST_CHECK_TYPE(tt::common_type<UDT volatile()>::type, UDT volatile(*)());
     BOOST_CHECK_TYPE(tt::common_type<UDT const volatile()>::type, UDT const volatile(*)());
+#endif
 }
 TT_TEST_END