diff -u -r airsnort-0.2.4a/src/PacketSource.c airsnort-0.2.4a-new/src/PacketSource.c
--- airsnort-0.2.4a/src/PacketSource.c	Thu Mar 18 01:47:56 2004
+++ airsnort-0.2.4a-new/src/PacketSource.c	Thu Mar 18 16:53:45 2004
@@ -61,6 +61,8 @@
    PacketSource *src = (PacketSource*) calloc(sizeof(PacketSource), 1);
 #ifndef WIN32
    src->pcap = pcap_open_live(dev, snaplen, promisc, to_ms, errbuf);
+   if(src->pcap == 0)
+     return NULL;
    src->dlType = pcap_datalink(src->pcap);
 #else
    HANDLE hAdapter = 0;