diff --git a/tsock_v4.c b/tsock_v4.c
index afaaa0d..c54a4f1 100644
--- a/tsock_v4.c
+++ b/tsock_v4.c
@@ -135,7 +135,7 @@ int main (int argc, char **argv) {
     transport = 1;
   }
 
-  if (source == -1) {
+  if (source == -1 && ( (transport == 1 && client == 0) || transport == 0 ) ) {
     usage();
     exit(1) ;
   }