diff --git a/Inc/SerialPortFrameIO.h b/Inc/SerialPortFrameIO.h
index c118895..0f144d6 100644
--- a/Inc/SerialPortFrameIO.h
+++ b/Inc/SerialPortFrameIO.h
@@ -6,7 +6,7 @@
 #define MODULE_SERIALPORTFRAMEIO_H
 #include "stdint.h"
 
-typedef uint16_t (*SerialPortFrameIOTransaction  )(void *env, uint8_t u8MbIndex, uint8_t *data, uint16_t size, uint32_t timeout);
+typedef uint16_t (*SerialPortFrameIOTransaction  )(void *env, uint8_t *data, uint16_t size, uint32_t timeout);
 
 typedef struct {
     void *env;