diff --git a/src/core/ipv4/icmp.c b/src/core/ipv4/icmp.c
index 9a82a67a..f35ff4b5 100644
--- a/src/core/ipv4/icmp.c
+++ b/src/core/ipv4/icmp.c
@@ -213,6 +213,7 @@ icmp_input(struct pbuf *p, struct netif *inp)
         ip4_addr_copy(iphdr->src, *src);
         ip4_addr_copy(iphdr->dest, *ip4_current_src_addr());
         ICMPH_TYPE_SET(iecho, ICMP_ER);
+        p->if_idx = NETIF_NO_INDEX; /* we're reusing this pbuf, so reset its if_idx */
 #if CHECKSUM_GEN_ICMP
         IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_GEN_ICMP) {
           /* adjust the checksum */