diff --git a/ports/win32/pcap_helper.c b/ports/win32/pcap_helper.c
index f879044..698d011 100644
--- a/ports/win32/pcap_helper.c
+++ b/ports/win32/pcap_helper.c
@@ -60,5 +60,5 @@ get_adapter_index_from_addr(U32 netaddr, char *guid, U32 guid_len)
    printf("Network address not found.\n");
 
    pcap_freealldevs(alldevs);
-   return index;
+   return -1;
 }