diff --git a/include/boost/config/compiler/gcc.hpp b/include/boost/config/compiler/gcc.hpp
index 78f1ae39..d6fbda0e 100644
--- a/include/boost/config/compiler/gcc.hpp
+++ b/include/boost/config/compiler/gcc.hpp
@@ -254,7 +254,6 @@
 // C++0x features in 4.8.n and later
 //
 #if (BOOST_GCC_VERSION < 40800) || !defined(BOOST_GCC_CXX11)
-#  define BOOST_NO_CXX11_ALIGNAS
 #  define BOOST_NO_CXX11_THREAD_LOCAL
 #  define BOOST_NO_CXX11_SFINAE_EXPR
 #endif
@@ -267,6 +266,14 @@
 #  define BOOST_NO_CXX14_BINARY_LITERALS
 #endif
 
+// C++0x features in 4.9.n and later
+//
+#if (BOOST_GCC_VERSION < 40900) || !defined(BOOST_GCC_CXX11)
+// Although alignas support is added in gcc 4.8, it does not accept
+// constant expressions as an argument until gcc 4.9.
+#  define BOOST_NO_CXX11_ALIGNAS
+#endif
+
 // C++0x features in 5.1 and later
 //
 #if (BOOST_GCC_VERSION < 50100) || !defined(BOOST_GCC_CXX11)