diff --git a/src/bouncer/client.py b/src/bouncer/client.py
index ec13f3b..948b5dc 100644
--- a/src/bouncer/client.py
+++ b/src/bouncer/client.py
@@ -112,6 +112,15 @@ class Client:
         if msg.command == "QUIT":
             return
 
+        # Block direct NICK -- must go through /msg *bouncer NICK <network> <nick>
+        if msg.command == "NICK":
+            self._send_msg(IRCMessage(
+                command="NOTICE",
+                params=[self._nick, "Use /msg *bouncer NICK <network> <nick>"],
+                prefix="*bouncer!bouncer@bouncer",
+            ))
+            return
+
         # Intercept bouncer control commands
         if msg.command == "PRIVMSG" and len(msg.params) >= 2:
             target = msg.params[0].lower()