diff --git a/include/boost/operators.hpp b/include/boost/operators.hpp
index 7dce7df..be56a2f 100644
--- a/include/boost/operators.hpp
+++ b/include/boost/operators.hpp
@@ -112,6 +112,8 @@
 // Define BOOST_OPERATORS_CONSTEXPR to be like BOOST_CONSTEXPR but empty under MSVC < v19.22
 #if BOOST_WORKAROUND(BOOST_MSVC, < 1922)
 #define BOOST_OPERATORS_CONSTEXPR
+#elif defined __sun
+#define BOOST_OPERATORS_CONSTEXPR
 #else
 #define BOOST_OPERATORS_CONSTEXPR BOOST_CONSTEXPR
 #endif