diff --git a/src/beast/include/beast/core/detail/base64.hpp b/src/beast/include/beast/core/detail/base64.hpp
index 31b426a61e..9d29ca78b8 100644
--- a/src/beast/include/beast/core/detail/base64.hpp
+++ b/src/beast/include/beast/core/detail/base64.hpp
@@ -96,8 +96,7 @@ inline
 std::size_t constexpr
 decoded_size(std::size_t n)
 {
-    return n / 4 * 3; // requires n&3==0, smaller
-    //return 3 * n / 4;
+    return ((n / 4) * 3) + 2;
 }
 
 /** Encode a series of octets as a padded, base64 string.