diff --git a/lsm9ds1_reg.h b/lsm9ds1_reg.h
index d664c30..e46de36 100644
--- a/lsm9ds1_reg.h
+++ b/lsm9ds1_reg.h
@@ -109,10 +109,8 @@ typedef struct
   *
   */
 
-typedef int32_t (*stmdev_write_ptr)(void *, uint8_t, uint8_t *,
-                                    uint16_t);
-typedef int32_t (*stmdev_read_ptr)(void *, uint8_t, uint8_t *,
-                                   uint16_t);
+typedef int32_t (*stmdev_write_ptr)(void *, uint8_t, const uint8_t *, uint16_t);
+typedef int32_t (*stmdev_read_ptr)(void *, uint8_t, uint8_t *, uint16_t);
 
 typedef struct
 {