diff --git a/lib/xenu_nntp/mbox.py b/lib/xenu_nntp/mbox.py
index e77cedf..761bf0b 100644
--- a/lib/xenu_nntp/mbox.py
+++ b/lib/xenu_nntp/mbox.py
@@ -72,12 +72,15 @@ class MBoxReader():
             # We have reached the final message in the stream.
             #
             if line is None or line == '':
-                ret = self.message
-                ret.finish()
+                if self.message:
+                    ret = self.message
+                    ret.finish()
 
-                self.message = None
+                    self.message = None
 
-                return ret
+                    return ret
+
+                return None
 
             line = line.replace('\x00', '')