diff --git a/src/include/netif/ppp/ppp.h b/src/include/netif/ppp/ppp.h
index de740ec7..862b8269 100644
--- a/src/include/netif/ppp/ppp.h
+++ b/src/include/netif/ppp/ppp.h
@@ -427,6 +427,7 @@ struct ppp_pcb_s {
  * only be called while the PPP is in the dead phase (i.e. disconnected).
  */
 
+#if PPP_AUTH_SUPPORT
 /*
  * Set PPP authentication.
  *
@@ -458,7 +459,6 @@ struct ppp_pcb_s {
 #define PPPAUTHTYPE_ANY       0xff
 void ppp_set_auth(ppp_pcb *pcb, u8_t authtype, const char *user, const char *passwd);
 
-#if PPP_AUTH_SUPPORT
 /*
  * Whether peer is required to authenticate. This is mostly necessary for PPP server support.
  */
diff --git a/src/netif/ppp/ppp.c b/src/netif/ppp/ppp.c
index 7f7e9c3f..c0d2004b 100644
--- a/src/netif/ppp/ppp.c
+++ b/src/netif/ppp/ppp.c
@@ -209,8 +209,8 @@ static err_t ppp_netif_output(struct netif *netif, struct pbuf *pb, u16_t protoc
 /***********************************/
 /*** PUBLIC FUNCTION DEFINITIONS ***/
 /***********************************/
-void ppp_set_auth(ppp_pcb *pcb, u8_t authtype, const char *user, const char *passwd) {
 #if PPP_AUTH_SUPPORT
+void ppp_set_auth(ppp_pcb *pcb, u8_t authtype, const char *user, const char *passwd) {
 #if PAP_SUPPORT
   pcb->settings.refuse_pap = !(authtype & PPPAUTHTYPE_PAP);
 #endif /* PAP_SUPPORT */
@@ -226,13 +226,8 @@ void ppp_set_auth(ppp_pcb *pcb, u8_t authtype, const char *user, const char *pas
 #endif /* EAP_SUPPORT */
   pcb->settings.user = user;
   pcb->settings.passwd = passwd;
-#else /* PPP_AUTH_SUPPORT */
-  LWIP_UNUSED_ARG(pcb);
-  LWIP_UNUSED_ARG(authtype);
-  LWIP_UNUSED_ARG(user);
-  LWIP_UNUSED_ARG(passwd);
-#endif /* PPP_AUTH_SUPPORT */
 }
+#endif /* PPP_AUTH_SUPPORT */
 
 #if MPPE_SUPPORT
 /* Set MPPE configuration */