diff --git a/src/api/pppapi.c b/src/api/pppapi.c
index 08e7508e..daf3a483 100644
--- a/src/api/pppapi.c
+++ b/src/api/pppapi.c
@@ -349,7 +349,7 @@ pppapi_do_ppp_ioctl(struct pppapi_msg_msg *msg)
  * Call ppp_ioctl() in a thread-safe way by running that function inside the
  * tcpip_thread context.
  */
-int
+err_t
 pppapi_ioctl(ppp_pcb *pcb, int cmd, void *arg)
 {
   struct pppapi_msg msg;
diff --git a/src/include/lwip/pppapi.h b/src/include/lwip/pppapi.h
index aed14c6b..2adfa4ac 100644
--- a/src/include/lwip/pppapi.h
+++ b/src/include/lwip/pppapi.h
@@ -137,7 +137,7 @@ int pppapi_open(ppp_pcb *pcb, u16_t holdoff);
 int pppapi_close(ppp_pcb *pcb);
 void pppapi_sighup(ppp_pcb *pcb);
 int pppapi_free(ppp_pcb *pcb);
-int pppapi_ioctl(ppp_pcb *pcb, int cmd, void *arg);
+err_t pppapi_ioctl(ppp_pcb *pcb, int cmd, void *arg);
 #if LWIP_NETIF_STATUS_CALLBACK
 void pppapi_set_netif_statuscallback(ppp_pcb *pcb, netif_status_callback_fn status_callback);
 #endif /* LWIP_NETIF_STATUS_CALLBACK */
diff --git a/src/include/netif/ppp/ppp.h b/src/include/netif/ppp/ppp.h
index ec5eaf4f..e08455ff 100644
--- a/src/include/netif/ppp/ppp.h
+++ b/src/include/netif/ppp/ppp.h
@@ -494,7 +494,7 @@ int ppp_free(ppp_pcb *pcb);
  * Get and set parameters for the given connection.
  * Return 0 on success, an error code on failure. 
  */
-int ppp_ioctl(ppp_pcb *pcb, int cmd, void *arg);
+err_t ppp_ioctl(ppp_pcb *pcb, int cmd, void *arg);
 
 /* Get the PPP netif interface */
 #define ppp_netif(ppp)               (ppp->netif)
diff --git a/src/include/netif/ppp/ppp_impl.h b/src/include/netif/ppp/ppp_impl.h
index ddbc8934..d07e8acb 100644
--- a/src/include/netif/ppp/ppp_impl.h
+++ b/src/include/netif/ppp/ppp_impl.h
@@ -158,7 +158,7 @@ struct link_callbacks {
   /* configure TCP header compression */
   void (*vj_config)(ppp_pcb *pcb, void *ctx, int vjcomp, int cidcomp, int maxcid);
   /* Get and set parameters for the given connection. */
-  int (*ioctl)(ppp_pcb *pcb, void *ctx, int cmd, void *arg);
+  err_t (*ioctl)(ppp_pcb *pcb, void *ctx, int cmd, void *arg);
   /* Pass the processed input packet to the appropriate handler. */
   err_t (*netif_input)(ppp_pcb *pcb, void *ctx, struct pbuf *p, u16_t protocol);
 };
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index 5bd548e2..190732fc 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -337,11 +337,12 @@ int ppp_free(ppp_pcb *pcb) {
 
 /* Get and set parameters for the given connection.
  * Return 0 on success, an error code on failure. */
-int
+err_t
 ppp_ioctl(ppp_pcb *pcb, int cmd, void *arg)
 {
-  if(NULL == pcb)
-    return PPPERR_PARAM;
+  if (pcb == NULL) {
+    return ERR_VAL;
+  }
 
   switch(cmd) {
     case PPPCTLG_UPSTATUS:      /* Get the PPP up status. */
@@ -349,21 +350,21 @@ ppp_ioctl(ppp_pcb *pcb, int cmd, void *arg)
         goto fail;
       }
       *(int *)arg = (int)(pcb->if_up);
-      return PPPERR_NONE;
+      return ERR_OK;
 
     case PPPCTLS_ERRCODE:       /* Set the PPP error code. */
       if (!arg) {
         goto fail;
       }
       pcb->err_code = (u8_t)(*(int *)arg);
-      return PPPERR_NONE;
+      return ERR_OK;
 
     case PPPCTLG_ERRCODE:       /* Get the PPP error code. */
       if (!arg) {
         goto fail;
       }
       *(int *)arg = (int)(pcb->err_code);
-      return PPPERR_NONE;
+      return ERR_OK;
 
     default:
       if (pcb->link_cb->ioctl) {
@@ -372,7 +373,7 @@ ppp_ioctl(ppp_pcb *pcb, int cmd, void *arg)
   }
 
 fail:
-  return PPPERR_PARAM;
+  return ERR_VAL;
 }
 
 #if LWIP_NETIF_STATUS_CALLBACK
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index bad89436..8ee1c3c7 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -58,7 +58,7 @@ static void pppos_disconnect(ppp_pcb *ppp, void *ctx);
 static err_t pppos_destroy(ppp_pcb *ppp, void *ctx);
 static void pppos_send_config(ppp_pcb *ppp, void *ctx, u32_t accm);
 static void pppos_recv_config(ppp_pcb *ppp, void *ctx, u32_t accm);
-static int pppos_ioctl(ppp_pcb *pcb, void *ctx, int cmd, void *arg);
+static err_t pppos_ioctl(ppp_pcb *pcb, void *ctx, int cmd, void *arg);
 #if VJ_SUPPORT
 static void pppos_vjc_config(ppp_pcb *ppp, void *ctx, int vjcomp, int cidcomp, int maxcid);
 static err_t pppos_netif_input(ppp_pcb *ppp, void *ctx, struct pbuf *p, u16_t protocol);
@@ -753,7 +753,7 @@ pppos_recv_config(ppp_pcb *ppp, void *ctx, u32_t accm)
             pppos->in_accm[0], pppos->in_accm[1], pppos->in_accm[2], pppos->in_accm[3]));
 }
 
-static int
+static err_t
 pppos_ioctl(ppp_pcb *pcb, void *ctx, int cmd, void *arg)
 {
   pppos_pcb *pppos = (pppos_pcb *)ctx;
@@ -765,13 +765,13 @@ pppos_ioctl(ppp_pcb *pcb, void *ctx, int cmd, void *arg)
         goto fail;
       }
       *(sio_fd_t *)arg = pppos->fd;
-      return PPPERR_NONE;
+      return ERR_OK;
 
     default: ;
   }
 
 fail:
-  return PPPERR_PARAM;
+  return ERR_VAL;
 }
 
 #if VJ_SUPPORT