diff --git a/include/ecrt.h b/include/ecrt.h
index 0eeeddc6..315d4883 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -1974,8 +1974,9 @@ EC_PUBLIC_API int ecrt_domain_state(
  * set via ecrt_slave_config_create_sdo_request().
  *
  * \ingroup ApplicationInterfaceRT
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_sdo_request_index(
+EC_PUBLIC_API int ecrt_sdo_request_index(
         ec_sdo_request_t *req, /**< SDO request. */
         uint16_t index, /**< SDO index. */
         uint8_t subindex /**< SDO subindex. */
@@ -1991,8 +1992,9 @@ EC_PUBLIC_API void ecrt_sdo_request_index(
  *
  * The timeout should be defined in non-realtime context, but can also be
  * changed afterwards.
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_sdo_request_timeout(
+EC_PUBLIC_API int ecrt_sdo_request_timeout(
         ec_sdo_request_t *req, /**< SDO request. */
         uint32_t timeout /**< Timeout in milliseconds. Zero means no
                            timeout. */
@@ -2075,8 +2077,9 @@ ec_request_state_t ecrt_sdo_request_state(
  * activation).
  *
  * \ingroup ApplicationInterfaceRT
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_sdo_request_write(
+EC_PUBLIC_API int ecrt_sdo_request_write(
         ec_sdo_request_t *req /**< SDO request. */
         );
 
@@ -2093,8 +2096,9 @@ EC_PUBLIC_API void ecrt_sdo_request_write(
  * activation).
  *
  * \ingroup ApplicationInterfaceRT
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_sdo_request_read(
+EC_PUBLIC_API int ecrt_sdo_request_read(
         ec_sdo_request_t *req /**< SDO request. */
         );
 
diff --git a/lib/sdo_request.c b/lib/sdo_request.c
index 6271f642..509a349c 100644
--- a/lib/sdo_request.c
+++ b/lib/sdo_request.c
@@ -48,7 +48,7 @@ void ec_sdo_request_clear(ec_sdo_request_t *req)
  * Application interface.
  ****************************************************************************/
 
-void ecrt_sdo_request_index(ec_sdo_request_t *req, uint16_t index,
+int ecrt_sdo_request_index(ec_sdo_request_t *req, uint16_t index,
         uint8_t subindex)
 {
     ec_ioctl_sdo_request_t data;
@@ -61,14 +61,14 @@ void ecrt_sdo_request_index(ec_sdo_request_t *req, uint16_t index,
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SDO_REQUEST_INDEX, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to set SDO request index/subindex: %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_sdo_request_timeout(ec_sdo_request_t *req, uint32_t timeout)
+int ecrt_sdo_request_timeout(ec_sdo_request_t *req, uint32_t timeout)
 {
     ec_ioctl_sdo_request_t data;
     int ret;
@@ -79,9 +79,9 @@ void ecrt_sdo_request_timeout(ec_sdo_request_t *req, uint32_t timeout)
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SDO_REQUEST_TIMEOUT, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to set SDO request timeout: %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -139,7 +139,7 @@ ec_request_state_t ecrt_sdo_request_state(ec_sdo_request_t *req)
 
 /****************************************************************************/
 
-void ecrt_sdo_request_read(ec_sdo_request_t *req)
+int ecrt_sdo_request_read(ec_sdo_request_t *req)
 {
     ec_ioctl_sdo_request_t data;
     int ret;
@@ -149,14 +149,14 @@ void ecrt_sdo_request_read(ec_sdo_request_t *req)
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SDO_REQUEST_READ, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to command an SDO read operation : %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_sdo_request_write(ec_sdo_request_t *req)
+int ecrt_sdo_request_write(ec_sdo_request_t *req)
 {
     ec_ioctl_sdo_request_t data;
     int ret;
@@ -168,9 +168,9 @@ void ecrt_sdo_request_write(ec_sdo_request_t *req)
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SDO_REQUEST_WRITE, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to command an SDO write operation : %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
diff --git a/master/ioctl.c b/master/ioctl.c
index 4282bf85..04afb142 100644
--- a/master/ioctl.c
+++ b/master/ioctl.c
@@ -3459,8 +3459,7 @@ static ATTRIBUTES int ec_ioctl_sdo_request_index(
         return -ENOENT;
     }
 
-    ecrt_sdo_request_index(req, data.sdo_index, data.sdo_subindex);
-    return 0;
+    return ecrt_sdo_request_index(req, data.sdo_index, data.sdo_subindex);
 }
 
 /****************************************************************************/
@@ -3496,8 +3495,7 @@ static ATTRIBUTES int ec_ioctl_sdo_request_timeout(
         return -ENOENT;
     }
 
-    ecrt_sdo_request_timeout(req, data.timeout);
-    return 0;
+    return ecrt_sdo_request_timeout(req, data.timeout);
 }
 
 /****************************************************************************/
@@ -3580,8 +3578,7 @@ static ATTRIBUTES int ec_ioctl_sdo_request_read(
         return -ENOENT;
     }
 
-    ecrt_sdo_request_read(req);
-    return 0;
+    return ecrt_sdo_request_read(req);
 }
 
 /****************************************************************************/
@@ -3630,8 +3627,7 @@ static ATTRIBUTES int ec_ioctl_sdo_request_write(
         return -EFAULT;
 
     req->data_size = data.size;
-    ecrt_sdo_request_write(req);
-    return 0;
+    return ecrt_sdo_request_write(req);
 }
 
 /****************************************************************************/
diff --git a/master/sdo_request.c b/master/sdo_request.c
index d0de57db..040c6b5d 100644
--- a/master/sdo_request.c
+++ b/master/sdo_request.c
@@ -178,18 +178,20 @@ int ec_sdo_request_timed_out(const ec_sdo_request_t *req /**< SDO request. */)
  * Application interface.
  ****************************************************************************/
 
-void ecrt_sdo_request_index(ec_sdo_request_t *req, uint16_t index,
+int ecrt_sdo_request_index(ec_sdo_request_t *req, uint16_t index,
         uint8_t subindex)
 {
     req->index = index;
     req->subindex = subindex;
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_sdo_request_timeout(ec_sdo_request_t *req, uint32_t timeout)
+int ecrt_sdo_request_timeout(ec_sdo_request_t *req, uint32_t timeout)
 {
     req->issue_timeout = timeout;
+    return 0;
 }
 
 /****************************************************************************/
@@ -215,24 +217,26 @@ ec_request_state_t ecrt_sdo_request_state(const ec_sdo_request_t *req)
 
 /****************************************************************************/
 
-void ecrt_sdo_request_read(ec_sdo_request_t *req)
+int ecrt_sdo_request_read(ec_sdo_request_t *req)
 {
     req->dir = EC_DIR_INPUT;
     req->state = EC_INT_REQUEST_QUEUED;
     req->errno = 0;
     req->abort_code = 0x00000000;
     req->jiffies_start = jiffies;
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_sdo_request_write(ec_sdo_request_t *req)
+int ecrt_sdo_request_write(ec_sdo_request_t *req)
 {
     req->dir = EC_DIR_OUTPUT;
     req->state = EC_INT_REQUEST_QUEUED;
     req->errno = 0;
     req->abort_code = 0x00000000;
     req->jiffies_start = jiffies;
+    return 0;
 }
 
 /****************************************************************************/