diff --git a/src/core/ipv4/icmp.c b/src/core/ipv4/icmp.c
index c866663b..dbf7349c 100644
--- a/src/core/ipv4/icmp.c
+++ b/src/core/ipv4/icmp.c
@@ -380,7 +380,7 @@ icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
   {
     ip4_addr_t iphdr_dst;
     ip4_addr_copy(iphdr_dst, iphdr->dest);
-    netif = ip4_route_src(&iphdr_src, &iphdr_dst);
+    netif = ip4_route_src(&iphdr_dst, &iphdr_src);
   }
 #else
   netif = ip4_route(&iphdr_src);
diff --git a/src/core/udp.c b/src/core/udp.c
index f7ac596c..553f6fb6 100644
--- a/src/core/udp.c
+++ b/src/core/udp.c
@@ -539,7 +539,7 @@ udp_sendto_chksum(struct udp_pcb *pcb, struct pbuf *p, const ip_addr_t *dst_ip,
            fails, we try regular routing as though no override was set. */
         if (!ip4_addr_isany_val(pcb->mcast_ip4) &&
             !ip4_addr_cmp(&pcb->mcast_ip4, IP4_ADDR_BROADCAST)) {
-          netif = ip4_route_src(ip_2_ip4(&pcb->local_ip), &pcb->mcast_ip4);
+          netif = ip4_route_src(&pcb->mcast_ip4, ip_2_ip4(&pcb->local_ip));
         }
       }
 #endif /* LWIP_IPV4 */