diff --git a/Inc/AdcIO.h b/Inc/AdcIO.h
index 21ceab0..6e39803 100644
--- a/Inc/AdcIO.h
+++ b/Inc/AdcIO.h
@@ -7,7 +7,7 @@
 
 #include "stdint.h"
 
-typedef uint8_t (*AdcIOTransaction  )(void *env, uint32_t *buf, uint32_t timeout);
+typedef uint32_t (*AdcIOTransaction  )(void *env, uint32_t *buf, uint32_t timeout);
 
 typedef struct {
     void *env;