diff -r a26dee45c467 -r 1aee02c1e294 lib/master.c
--- a/lib/master.c	Sat May 31 17:21:53 2014 +1200
+++ b/lib/master.c	Sat May 31 18:08:27 2014 +1200
@@ -390,7 +390,7 @@
 /****************************************************************************/
 
 int ecrt_master_sdo_download(ec_master_t *master, uint16_t slave_position,
-        uint16_t index, uint8_t subindex, uint8_t *data,
+        uint16_t index, uint8_t subindex, const uint8_t *data,
         size_t data_size, uint32_t *abort_code)
 {
     ec_ioctl_slave_sdo_download_t download;
@@ -419,7 +419,7 @@
 /****************************************************************************/
 
 int ecrt_master_sdo_download_complete(ec_master_t *master,
-        uint16_t slave_position, uint16_t index, uint8_t *data,
+        uint16_t slave_position, uint16_t index, const uint8_t *data,
         size_t data_size, uint32_t *abort_code)
 {
     ec_ioctl_slave_sdo_download_t download;