diff --git a/lib/nntp/tiny/session.py b/lib/nntp/tiny/session.py
index d82c137..e10be96 100644
--- a/lib/nntp/tiny/session.py
+++ b/lib/nntp/tiny/session.py
@@ -19,6 +19,9 @@ class SessionState(enum.Flag):
     AUTH_OK   = enum.auto()
     AUTH_POST = enum.auto()
 
+class SessionMode(enum.Enum):
+    READER = 1
+
 class MessagePart(enum.Enum):
     HEAD  = 1
     BODY  = enum.auto()
@@ -104,9 +107,10 @@ class Session():
     def __init__(self, server: Server, sock: socket.socket):
         self.server: Server      = server
         self.db: Database        = server.db
-        self.state: SessionState = SessionState.ACTIVE
         self.sock: socket.socket = sock
         self.buf: LineBuffer     = LineBuffer()
+        self.state: SessionState = SessionState.ACTIVE
+        self.mode: SessionMode   = SessionMode.READER
 
         self.newsgroup:  Optional[Newsgroup] = None
         self.article_id: Optional[int]       = None
@@ -139,6 +143,14 @@ class Session():
 
         self.end()
 
+    def _cmd_mode(self, *args):
+        if len(args) != 1 or args[0] != 'READER':
+            return self.respond(ResponseCode.NNTP_SYNTAX_ERROR)
+
+        self.mode = SessionMode.READER
+
+        return self.respond(ResponseCode.NNTP_POST_PROHIBITED)
+
     def _cmd_group(self, name: str):
         if name not in self.server.newsgroups:
             return self.respond(ResponseCode.NNTP_NEWSGROUP_NOT_FOUND)
@@ -561,6 +573,7 @@ class Session():
 
     COMMANDS = {
         'CAPABILITIES': _cmd_capabilities,
+        'MODE':         _cmd_mode,
         'GROUP':        _cmd_group,
         'LISTGROUP':    _cmd_listgroup,
         'LIST':         _cmd_list,