diff --git md5.h md5.h
index d8b96df..86103da 100644
--- md5.h
+++ md5.h
@@ -124,6 +124,13 @@ private:
 #include CRYPTOPP_INCLUDE_MD5
 #endif

+#if (CRYPTOPP_VERSION >= 600) && (__cplusplus >= 201103L)
+  using byte = CryptoPP::byte;
+#else
+  typedef unsigned char byte;
+#endif
+
+
 class MD5 {

 public:
@@ -151,4 +158,4 @@ private:

 #endif //DO_NOT_USE_CRYPTOPP_MD5

-#endif //MD5_H
\ No newline at end of file
+#endif //MD5_H