diff --git a/src/lib/dhcp/option_definition.h b/src/lib/dhcp/option_definition.h
index cc8b4951cf..878abeb35f 100644
--- a/src/lib/dhcp/option_definition.h
+++ b/src/lib/dhcp/option_definition.h
@@ -310,6 +310,10 @@ public:
     /// @param type option type.
     /// @param begin beginning of the option buffer.
     /// @param end end of the option buffer.
+    /// @param callback An instance of the function which parses packet options.
+    /// If this is set to non NULL value this function will be used instead of
+    /// @c isc::dhcp::LibDHCP::unpackOptions6 and
+    /// isc::dhcp::LibDHCP::unpackOptions4.
     ///
     /// @return instance of the DHCP option.
     /// @throw InvalidOptionValue if data for the option is invalid.
@@ -331,6 +335,10 @@ public:
     /// @param u option universe (V4 or V6).
     /// @param type option type.
     /// @param buf option buffer.
+    /// @param callback An instance of the function which parses packet options.
+    /// If this is set to non NULL value this function will be used instead of
+    /// @c isc::dhcp::LibDHCP::unpackOptions6 and
+    /// isc::dhcp::LibDHCP::unpackOptions4.
     ///
     /// @return instance of the DHCP option.
     /// @throw InvalidOptionValue if data for the option is invalid.
@@ -439,8 +447,15 @@ public:
     ///
     /// @param u universe (V4 or V6).
     /// @param type option type.
+    /// @param encapsulated_space An option space being encapsulated by the
+    /// options created by this factory function. The options which belong to
+    /// encapsulated option space are sub options of this option.
     /// @param begin iterator pointing to the beginning of the buffer.
     /// @param end iterator pointing to the end of the buffer.
+    /// @param callback An instance of the function which parses packet options.
+    /// If this is set to non NULL value this function will be used instead of
+    /// @c isc::dhcp::LibDHCP::unpackOptions6 and
+    /// isc::dhcp::LibDHCP::unpackOptions4.
     /// @tparam T type of the data field (must be one of the uintX_t or intX_t).
     ///
     /// @throw isc::OutOfRange if provided option buffer length is invalid.