diff --git a/fluent/sender.py b/fluent/sender.py
index 72e8c36..68e86d5 100644
--- a/fluent/sender.py
+++ b/fluent/sender.py
@@ -122,7 +122,7 @@ def close(self):
 
     def _make_packet(self, label, timestamp, data):
         if label:
-            tag = '.'.join((self.tag, label))
+            tag = '.'.join((self.tag, label)) if self.tag else label
         else:
             tag = self.tag
         packet = (tag, timestamp, data)