diff --git a/doc/prefixing.md b/doc/prefixing.md
index 08ef3b6..d432cb2 100644
--- a/doc/prefixing.md
+++ b/doc/prefixing.md
@@ -9,6 +9,17 @@ In some commands (like PRIVMSG, TOPIC, USER, NOTICE, etc), the client needs to a
 ↗️ PRIVMSG foo this is a very cool message
 🔀 nick!ident@host PRIVMSG foo :this
 ```
+The server will only detect the first word
+
+
+❌ Your client shouldn't do this either:
+```
+↗️ PRIVMSG foo: this is a very cool message
+↙️ :server 401 nick foo: :No such nick/channel
+```
+The server will think that the nickname ends with a colon.
+
+
 ✅ Here's what it should do:
 ```
 ↗️ PRIVMSG foo :this is a very cool message