diff --git a/include/ecrt.h b/include/ecrt.h
index 8416c172c7c111d501b7d8aa54d01e9416fa2e23..0f1a819f2f1fa966f64d5e99cffadd7f2848a000 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -145,6 +145,8 @@ int ecrt_domain_state(ec_domain_t *domain);
  *  Slave Methods
  *****************************************************************************/
 
+/* there SDO functions are deprecated! */
+
 int ecrt_slave_sdo_read_exp8(ec_slave_t *slave, uint16_t sdo_index,
                               uint8_t sdo_subindex, uint8_t *value);
 int ecrt_slave_sdo_read_exp16(ec_slave_t *slave, uint16_t sdo_index,
diff --git a/master/mailbox.c b/master/mailbox.c
index 8e62efdf54b2ddeac99ad90b9c69751b1cd5841a..ad4c1bcc967fb8ed70e83c812247e25ba66717b7 100644
--- a/master/mailbox.c
+++ b/master/mailbox.c
@@ -79,7 +79,7 @@ uint8_t *ec_slave_mbox_prepare_send(ec_slave_t *slave, /**< slave */
 
     EC_WRITE_U16(command->data,     size); // mailbox service data length
     EC_WRITE_U16(command->data + 2, slave->station_address); // station address
-    EC_WRITE_U8 (command->data + 4, 0x00); // hhannel & priority
+    EC_WRITE_U8 (command->data + 4, 0x00); // channel & priority
     EC_WRITE_U8 (command->data + 5, type); // underlying protocol type
 
     return command->data + 6;