diff --git a/src/include/netif/ppp/ppp_impl.h b/src/include/netif/ppp/ppp_impl.h
index 8a531262..07362ea6 100644
--- a/src/include/netif/ppp/ppp_impl.h
+++ b/src/include/netif/ppp/ppp_impl.h
@@ -155,8 +155,10 @@ struct link_callbacks {
   void (*send_config)(ppp_pcb *pcb, void *ctx, u32_t accm);
   /* confire the receive-side characteristics of the PPP interface */
   void (*recv_config)(ppp_pcb *pcb, void *ctx, u32_t accm);
+#if VJ_SUPPORT
   /* configure TCP header compression */
   void (*vj_config)(ppp_pcb *pcb, void *ctx, int vjcomp, int cidcomp, int maxcid);
+#endif /* VJ_SUPPORT */
   /* Get and set parameters for the given connection. */
   err_t (*ioctl)(ppp_pcb *pcb, void *ctx, int cmd, void *arg);
   /* Pass the processed input packet to the appropriate handler. */
diff --git a/src/netif/ppp/pppoe.c b/src/netif/ppp/pppoe.c
index 8a57dbbd..b974d415 100644
--- a/src/netif/ppp/pppoe.c
+++ b/src/netif/ppp/pppoe.c
@@ -156,7 +156,9 @@ static const struct link_callbacks pppoe_callbacks = {
   pppoe_netif_output,
   NULL,
   NULL,
+#if VJ_SUPPORT
   NULL,
+#endif /* VJ_SUPPORT */
   NULL,
   NULL
 };
diff --git a/src/netif/ppp/pppol2tp.c b/src/netif/ppp/pppol2tp.c
index 99a67a4f..8debc213 100644
--- a/src/netif/ppp/pppol2tp.c
+++ b/src/netif/ppp/pppol2tp.c
@@ -105,7 +105,9 @@ static const struct link_callbacks pppol2tp_callbacks = {
   pppol2tp_netif_output,
   NULL,
   NULL,
+#if VJ_SUPPORT
   NULL,
+#endif /* VJ_SUPPORT */
   NULL,
   NULL
 };
diff --git a/src/netif/ppp/pppos.c b/src/netif/ppp/pppos.c
index 4b857b0f..f41002f3 100644
--- a/src/netif/ppp/pppos.c
+++ b/src/netif/ppp/pppos.c
@@ -84,8 +84,6 @@ static const struct link_callbacks pppos_callbacks = {
   pppos_recv_config,
 #if VJ_SUPPORT
   pppos_vjc_config,
-#else /* VJ_SUPPORT */
-  NULL,
 #endif /* VJ_SUPPORT */
   pppos_ioctl,
 #if VJ_SUPPORT