diff --git a/src/netif/ppp/pppoe.c b/src/netif/ppp/pppoe.c
index 48251f4e..2394baa7 100644
--- a/src/netif/ppp/pppoe.c
+++ b/src/netif/ppp/pppoe.c
@@ -389,7 +389,9 @@ pppoe_disc_input(struct netif *netif, struct pbuf *pb)
   u16_t tag, len;
   u16_t session, plen;
   struct pppoe_softc *sc;
-  const char *err_msg;
+#if PPP_DEBUG
+  const char *err_msg = NULL;
+#endif /* PPP_DEBUG */
   u8_t *ac_cookie;
   u16_t ac_cookie_len;
 #ifdef PPPOE_SERVER
@@ -409,7 +411,6 @@ pppoe_disc_input(struct netif *netif, struct pbuf *pb)
 
   pb = ppp_singlebuf(pb);
 
-  err_msg = NULL;
   if (pb->len < sizeof(*ethhdr)) {
     goto done;
   }
@@ -479,6 +480,7 @@ pppoe_disc_input(struct netif *netif, struct pbuf *pb)
           ac_cookie_len = len;
         }
         break;
+#if PPP_DEBUG
       case PPPOE_TAG_SNAME_ERR:
         err_msg = "SERVICE NAME ERROR";
         break;
@@ -488,6 +490,7 @@ pppoe_disc_input(struct netif *netif, struct pbuf *pb)
       case PPPOE_TAG_GENERIC_ERR:
         err_msg = "GENERIC ERROR";
         break;
+#endif /* PPP_DEBUG */
       default:
         break;
     }
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index 9d474ca8..5fc48ede 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -866,6 +866,9 @@ static void
 pppos_vjc_config(ppp_pcb *ppp, void *ctx, int vjcomp, int cidcomp, int maxcid)
 {
   pppos_pcb *pppos = (pppos_pcb *)ctx;
+#if !PPP_DEBUG
+  LWIP_UNUSED_ARG(ppp);
+#endif /* !PPP_DEBUG */
 
   pppos->vj_enabled = vjcomp;
   pppos->vj_comp.compressSlot = cidcomp;
@@ -879,6 +882,9 @@ pppos_netif_input(ppp_pcb *ppp, void *ctx, struct pbuf *p, u16_t protocol)
 {
   int ret;
   pppos_pcb *pppos = (pppos_pcb *)ctx;
+#if !PPP_DEBUG
+  LWIP_UNUSED_ARG(ppp);
+#endif /* !PPP_DEBUG */
 
   switch(protocol) {
     case PPP_VJC_COMP:      /* VJ compressed TCP */