diff --git a/src/core/ipv4/igmp.c b/src/core/ipv4/igmp.c
index 39d9adc4..28f43db1 100644
--- a/src/core/ipv4/igmp.c
+++ b/src/core/ipv4/igmp.c
@@ -339,6 +339,9 @@ igmp_joingroup(struct netif *ifp, struct ip_addr *groupaddr)
 {
   struct igmp_group *group;
 
+  /* make sure netif is valid */
+  LWIP_ERROR("igmp_joingroup: attempt to join on NULL netif", (ifp!=NULL), return ERR_VAL;);
+
   /* make sure it is multicast address */
   LWIP_ERROR("igmp_joingroup: attempt to join non-multicast address", ip_addr_ismulticast(groupaddr), return ERR_VAL;);
 
@@ -387,6 +390,9 @@ igmp_leavegroup(struct netif *ifp, struct ip_addr *groupaddr)
 {
   struct igmp_group *group;
 
+  /* make sure netif is valid */
+  LWIP_ERROR("igmp_leavegroup: attempt to leave on NULL netif", (ifp!=NULL), return ERR_VAL;);
+
   /* make sure it is multicast address */
   LWIP_ERROR("igmp_leavegroup: attempt to leave non-multicast address", ip_addr_ismulticast(groupaddr), return ERR_VAL;);