diff --git a/src/netif/ethernet.c b/src/netif/ethernet.c
index 4596b32c..7270cfd8 100644
--- a/src/netif/ethernet.c
+++ b/src/netif/ethernet.c
@@ -94,6 +94,10 @@ ethernet_input(struct pbuf *p, struct netif *netif)
     goto free_and_return;
   }
 
+  if (p->if_idx == NETIF_NO_INDEX) {
+    p->if_idx = netif_get_index(netif);
+  }
+
   /* points to packet payload, which starts with an Ethernet header */
   ethhdr = (struct eth_hdr *)p->payload;
   LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE,