diff --git a/src/encoding/encoder.hpp b/src/encoding/encoder.hpp
index f5f40ae..a8092d1 100644
--- a/src/encoding/encoder.hpp
+++ b/src/encoding/encoder.hpp
@@ -159,6 +159,7 @@
 
   /**
    * @brief Reserve @p size bytes for the underlying buffer
+   * @param size amount of bytes to reserve in the underlying buffer
    * @param addInFront if true, then @p size bytes will be available in front (i.e., subsequent call
    *        to prepend* will not need to allocate memory).  If false, then reservation will be done
    *        at the end of the buffer (i.d., for subsequent append* calls)