diff --git a/server/src/hardware/protocol/z21/messages.hpp b/server/src/hardware/protocol/z21/messages.hpp
index bad3379c..31d99a85 100644
--- a/server/src/hardware/protocol/z21/messages.hpp
+++ b/server/src/hardware/protocol/z21/messages.hpp
@@ -512,7 +512,7 @@ struct LanXSetLocoFunction : LanX
   uint8_t db0 = 0xf8;
   uint8_t addressHigh;
   uint8_t addressLow;
-  uint8_t db3;
+  uint8_t db3 = 0;
   uint8_t checksum;
 
   LanXSetLocoFunction() :