diff --git a/impl.hpp b/impl.hpp
index d8af32d..520a7e0 100644
--- a/impl.hpp
+++ b/impl.hpp
@@ -18,7 +18,8 @@
     ASCII, /**< data encoded in ascii */
     RAW,   /**< raw data */
     // Keywords needing custom decoding
-    B1     /**< The keyword B1 needs to be decoded specially */
+    B1,     /**< The keyword B1 needs to be decoded specially */
+    UD      /**< Special decoding of UD meant for UUID */
 };
 
 } // namespace keyword