diff --git a/src/include/netif/ppp/mppe.h b/src/include/netif/ppp/mppe.h
index e5461324..6bf3ccde 100644
--- a/src/include/netif/ppp/mppe.h
+++ b/src/include/netif/ppp/mppe.h
@@ -173,7 +173,9 @@ void mppe_comp_reset(ppp_pcb *pcb, ppp_mppe_state *state);
 err_t mppe_compress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb, u16_t protocol);
 void mppe_decomp_reset(ppp_pcb *pcb, ppp_mppe_state *state);
 err_t mppe_decompress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb);
+#if 0 /* unused */
 void mppe_incomp(ppp_pcb *pcb, ppp_mppe_state *state, unsigned char *ibuf, int icnt);
+#endif /* unused */
 
 #endif /* MPPE_H */
 #endif /* PPP_SUPPORT && MPPE_SUPPORT */
diff --git a/src/netif/ppp/mppe.c b/src/netif/ppp/mppe.c
index f199a8bc..751f877c 100644
--- a/src/netif/ppp/mppe.c
+++ b/src/netif/ppp/mppe.c
@@ -389,6 +389,7 @@ mppe_decompress(ppp_pcb *pcb, ppp_mppe_state *state, struct pbuf **pb)
 	return ERR_OK;
 }
 
+#if 0 /* unused */
 /*
  * Incompressible data has arrived (this should never happen!).
  * We should probably drop the link if the protocol is in the range
@@ -406,5 +407,6 @@ void mppe_incomp(ppp_pcb *pcb, ppp_mppe_state *state, unsigned char *ibuf, int i
 		       "(proto %04x)\n", pcb->netif->num, PPP_PROTOCOL(ibuf)));
 	}
 }
+#endif /* unused */
 
 #endif /* PPP_SUPPORT && MPPE_SUPPORT */