diff --git a/lib/nntp/tiny/message.py b/lib/nntp/tiny/message.py
index f29b868..e6defd7 100644
--- a/lib/nntp/tiny/message.py
+++ b/lib/nntp/tiny/message.py
@@ -187,7 +187,7 @@ class Message(DatabaseTable):
         self.headers['subject'] = value
 
     def is_first_line(self):
-        return len(self.headers) == 1 and (self.body == '' or self.body is None)
+        return len(self.headers) == 1 and (self._body == '' or self._body is None)
 
     def read_line(self, line: str):
         if self.line is not None:
@@ -210,10 +210,10 @@ class Message(DatabaseTable):
 
                     self._headers[self._key] = decode(match[2].rstrip())
         elif self.state is MessageState.BODY:
-            if self.body is None:
-                self.body = ''
+            if self._body is None:
+                self._body = ''
             else:
-                self.body += self.line
+                self._body += self.line
 
         self.line = line