diff --git a/EduNetworkBuilder/NetworkInterface.cs b/EduNetworkBuilder/NetworkInterface.cs
index 99ab2ed..5e3387d 100644
--- a/EduNetworkBuilder/NetworkInterface.cs
+++ b/EduNetworkBuilder/NetworkInterface.cs
@@ -281,7 +281,7 @@ namespace EduNetworkBuilder
             NetworkCard nic = HD.NicFromID(AttachedToHostNic);
             if(nic != null && nic.GetNicType != NicType.port && nic.GetNicType != NicType.wport)
                 tPacket.TsourceIP = myIP;
-            if(tPacket.TsourceIP == null || tPacket.TsourceIP.GetIPString == NB.ZeroIPString)
+            if(tPacket.TsourceIP == null || tPacket.TsourceIP.IsZeroString())
                 tPacket.TsourceIP = myIP;
 
             if (What == VLANTagType.Forbidden)