diff --git a/lib/server/connection.ml b/lib/server/connection.ml
index 98557d4..d90238f 100644
--- a/lib/server/connection.ml
+++ b/lib/server/connection.ml
@@ -299,14 +299,15 @@ let on_msg_join t name =
   Ok ()
 
 let part user chan ~router ~reason =
+  let mem = Router.membership chan user in
   begin
-    let mem = Router.membership chan user in
-
-    Option.iter
-      (fun reason ->
-         let msg = Irc.Msg.make "PART" [Chan.name chan; reason] in
-         Router.relay msg ~from:user [`to_chan chan; `to_self])
-      reason;
+    if User.is_registered user ~router then
+      begin
+        let always_trailing = Option.is_some reason in
+        let reason = Option.to_list reason in
+        let msg = Irc.Msg.make "PART" (Chan.name chan :: reason) ~always_trailing in
+        Router.relay msg ~from:user [`to_chan chan; `to_self];
+      end;
 
     Router.part mem;
 
@@ -319,7 +320,11 @@ let part user chan ~router ~reason =
       end
   end
 
-let on_msg_part t name =
+let on_msg_part t name reason =
+  let reason = match reason with
+    | [] -> None
+    | xs -> Some (String.concat " " xs)
+  in
   let* me = require_registered t in
   let* chan =
     try
@@ -330,7 +335,7 @@ let on_msg_part t name =
       Error (nosuchchannel name)
   in
   try
-    part me chan ~router:t.router ~reason:(Some "Parting");
+    part me chan ~router:t.router ~reason;
     Ok ()
   with Not_found ->
     Error (notonchannel name)
@@ -375,11 +380,11 @@ let quit t me ~reason =
     let msg = Irc.Msg.make "QUIT" [User.nick me; reason] ~always_trailing:true in
     Router.relay msg ~from:me [`to_interested];
 
+    User.unregister me ~router:t.router;
     List.iter
       (part me ~router:t.router ~reason:None)
       (User.channels me);
 
-    User.unregister me ~router:t.router;
     t.user <- None
   end
 
@@ -388,9 +393,6 @@ let close ?(reason = "Client closed") t =
   Outbox.close t.outbox
 
 let on_msg_quit t reason =
-  (* TODO: '''When connections are terminated by a client-sent QUIT command, servers
-     SHOULD prepend <reason> with the ASCII string "Quit: " when sending QUIT messages to
-     other clients''' *)
   let reason = match reason with
     | [] -> "Quit"
     | xs -> String.concat " " ("Quit:" :: xs)
@@ -472,7 +474,7 @@ let dispatch t = function
   | "PRIVMSG", tgt :: msg :: _ -> on_msg_privmsg t tgt msg
   | "JOIN", tgt :: _ when tgt <> "" -> on_msg_join t tgt
   | "NAMES", tgt :: _ when tgt <> "" -> on_msg_names t tgt
-  | "PART", tgt :: _ when tgt <> "" -> on_msg_part t tgt
+  | "PART", tgt :: reason when tgt <> "" -> on_msg_part t tgt reason
   | "MODE", tgt :: args when tgt <> "" -> on_msg_mode t tgt args
   | ("USER" | "JOIN" | "NAMES" | "PART" | "MODE") as cmd, _ ->
     Error (needmoreparams cmd)