diff --git a/src/logic/error_codes.h b/src/logic/error_codes.h
index 8b8a00d..c02cc06 100644
--- a/src/logic/error_codes.h
+++ b/src/logic/error_codes.h
@@ -28,7 +28,10 @@ enum class ErrorCode : uint_fast16_t {
 
     INVALID_TOOL = 0x8006, ///< tool/slot index out of range (typically issuing T5 into an MMU with just 5 slots - valid range 0-4)
 
-    QUEUE_FULL = 0x802d, ///< internal logic error - attempt to move with a full queue
+    QUEUE_FULL = 0x802b, ///< internal logic error - attempt to move with a full queue
+
+    VERSION_MISMATCH = 0x802c, ///< internal error of the printer - incompatible version of the MMU FW
+    PROTOCOL_ERROR = 0x802d, ///< internal error of the printer - communication with the MMU got garbled - protocol decoder couldn't decode the incoming messages
     MMU_NOT_RESPONDING = 0x802e, ///< internal error of the printer - communication with the MMU is not working
     INTERNAL = 0x802f, ///< internal runtime error (software)