diff --git a/EduNetworkBuilder/NetworkCard.cs b/EduNetworkBuilder/NetworkCard.cs
index 773bc0c..97ee23f 100644
--- a/EduNetworkBuilder/NetworkCard.cs
+++ b/EduNetworkBuilder/NetworkCard.cs
@@ -707,7 +707,7 @@ namespace EduNetworkBuilder
                         nl = myNet.GetLinkFromID(ConnectedLink);
                         if (nl == null)
                             break;
-                        if (nPacket.sourceIP.GetIPString == NB.ZeroIPString && tPacket.MyType != PacketType.dhcp_request) return false; //We still have no IP.  Do not send the packet out.
+                        if ((nPacket.sourceIP == null || nPacket.sourceIP.GetIPString == NB.ZeroIPString) && tPacket.MyType != PacketType.dhcp_request) return false; //We still have no IP.  Do not send the packet out.
                         nPacket.StartOnLink(nl, WhereFrom); //This sends the packet down the link.
                         myNet.addPacket(nPacket);
                         if (tPacket.isFresh)