diff --git a/command/sol_cmds.hpp b/command/sol_cmds.hpp
index 010a245..2b0a55a 100644
--- a/command/sol_cmds.hpp
+++ b/command/sol_cmds.hpp
@@ -20,7 +20,7 @@
  *
  *  @return Response data for the command.
  */
-std::vector<uint8_t> payloadHandler(std::vector<uint8_t>& inPayload,
+std::vector<uint8_t> payloadHandler(const std::vector<uint8_t>& inPayload,
                                     const message::Handler& handler);
 
 constexpr uint8_t netfnTransport = 0x0C;