diff --git a/config.compat b/config.compat
index 65945d73..42d57c5f 100644
--- a/config.compat
+++ b/config.compat
@@ -922,7 +922,7 @@ NAMESPACE_END
 
 // http://stackoverflow.com/a/13867690/608639
 #if defined(CRYPTOPP_CXX11_CONSTEXPR)
-#  define CRYPTOPP_STATIC_CONSTEXPR static constexpr
+#  define CRYPTOPP_STATIC_CONSTEXPR static constexpr const
 #  define CRYPTOPP_CONSTEXPR constexpr
 #else
 #  define CRYPTOPP_STATIC_CONSTEXPR static const
diff --git a/config.h b/config.h
index 64d77f8e..c0383fb6 100644
--- a/config.h
+++ b/config.h
@@ -922,7 +922,7 @@ NAMESPACE_END
 
 // http://stackoverflow.com/a/13867690/608639
 #if defined(CRYPTOPP_CXX11_CONSTEXPR)
-#  define CRYPTOPP_STATIC_CONSTEXPR static constexpr
+#  define CRYPTOPP_STATIC_CONSTEXPR static constexpr const
 #  define CRYPTOPP_CONSTEXPR constexpr
 #else
 #  define CRYPTOPP_STATIC_CONSTEXPR static const