diff --git a/src/include/netif/ppp/ppp_impl.h b/src/include/netif/ppp/ppp_impl.h
index 480760a8..106baa60 100644
--- a/src/include/netif/ppp/ppp_impl.h
+++ b/src/include/netif/ppp/ppp_impl.h
@@ -432,7 +432,7 @@ struct pbuf *ppp_singlebuf(struct pbuf *p);
  */
 
 /* function called by all PPP subsystems to send packets */
-int ppp_write(ppp_pcb *pcb, struct pbuf *p);
+err_t ppp_write(ppp_pcb *pcb, struct pbuf *p);
 
 /* functions called by auth.c link_terminated() */
 void ppp_link_terminated(ppp_pcb *pcb);
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index 0dc1f808..f82ab62e 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -881,7 +881,7 @@ struct pbuf *ppp_singlebuf(struct pbuf *p) {
  *  RETURN: >= 0 Number of characters written
  *           -1 Failed to write to device
  */
-int ppp_write(ppp_pcb *pcb, struct pbuf *p) {
+err_t ppp_write(ppp_pcb *pcb, struct pbuf *p) {
 #if PRINTPKT_SUPPORT
   ppp_dump_packet("sent", (unsigned char *)p->payload+2, p->len-2);
 #endif /* PRINTPKT_SUPPORT */