diff --git a/weaver/main.go b/weaver/main.go
index eb8fc476..c1a26221 100644
--- a/weaver/main.go
+++ b/weaver/main.go
@@ -92,6 +92,9 @@ func main() {
 	}
 
 	if routerName == "" {
+		if iface == nil {
+			log.Fatal("Either an interface must be specified with -iface or a name with -name")
+		}
 		routerName = iface.HardwareAddr.String()
 	}