diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index 0c3092b..4dcbfb8 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -25,8 +25,16 @@
     /** Pointer to the correct image handler interface.  (nullptr on hash
      * blob_id) */
     ImageHandlerInterface* imageHandler;
+
+    /** The flags used to open the session. */
+    std::uint16_t flags;
 };
 
+struct ExtChunkHdr
+{
+    std::uint32_t length; /* Length of the data queued (little endian). */
+} __attribute__((packed));
+
 /**
  * Register only one firmware blob handler that will manage all sessions.
  */