diff --git a/src/include/netif/ppp/pppos.h b/src/include/netif/ppp/pppos.h
index 31abfa17..0401d9ff 100644
--- a/src/include/netif/ppp/pppos.h
+++ b/src/include/netif/ppp/pppos.h
@@ -102,7 +102,7 @@ ppp_pcb *pppos_create(struct netif *pppif, pppos_output_cb_fn output_cb,
 
 #if !NO_SYS && !PPP_INPROC_IRQ_SAFE
 /* Pass received raw characters to PPPoS to be decoded through lwIP TCPIP thread. */
-err_t pppos_input_tcpip(ppp_pcb *ppp, u8_t *s, int l);
+err_t pppos_input_tcpip(ppp_pcb *ppp, const void *s, int l);
 #endif /* !NO_SYS && !PPP_INPROC_IRQ_SAFE */
 
 /* PPP over Serial: this is the input function to be called for received data. */
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index f5fea002..1eb93430 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -422,7 +422,7 @@ pppos_destroy(ppp_pcb *ppp, void *ctx)
  * @param l length of received data
  */
 err_t
-pppos_input_tcpip(ppp_pcb *ppp, u8_t *s, int l)
+pppos_input_tcpip(ppp_pcb *ppp, const void *s, int l)
 {
   struct pbuf *p;
   err_t err;