diff --git a/degesch.c b/degesch.c
index 3c560be..acd4856 100644
--- a/degesch.c
+++ b/degesch.c
@@ -4357,27 +4357,6 @@ irc_handle_mode (struct server *s, const struct irc_message *msg)
 	refresh_prompt (s->ctx);
 }
 
-static struct buffer *
-irc_handle_buffer_collision (struct server *s,
-	struct buffer *buffer, const char *new_name)
-{
-	struct buffer *collision = str_map_find (&s->irc_buffer_map, new_name);
-	if (!collision)
-		return buffer;
-
-	// TODO: use full weechat-style buffer names
-	//   to prevent name collisions with the global buffer
-	hard_assert (collision->type == buffer->type);
-
-	// When there's a collision, there's not much else we can do
-	// other than somehow try to merge them
-	buffer_merge (s->ctx, collision, buffer);
-	if (s->ctx->current_buffer == buffer)
-		buffer_activate (s->ctx, collision);
-	buffer_remove (s->ctx, buffer);
-	return collision;
-}
-
 static void
 irc_handle_nick (struct server *s, const struct irc_message *msg)
 {
@@ -4392,17 +4371,16 @@ irc_handle_nick (struct server *s, const struct irc_message *msg)
 	if (!user)
 		return;
 
-	bool lexicographically_identical =
-		!irc_server_strcmp (s, user->nickname, new_nickname);
+	bool lexicographically_different =
+		!!irc_server_strcmp (s, user->nickname, new_nickname);
 
 	// What the fuck, someone renamed themselves to ourselves
 	// TODO: probably log a message and force a reconnect
-	if (!lexicographically_identical
+	if (lexicographically_different
 	 && !irc_server_strcmp (s, new_nickname, s->irc_user->nickname))
 		return;
 
-	// Log a message in any PM buffer and rename it;
-	// we may even have one for ourselves
+	// Log a message in any PM buffer (we may even have one for ourselves)
 	struct buffer *pm_buffer =
 		str_map_find (&s->irc_buffer_map, user->nickname);
 	if (pm_buffer)
@@ -4413,21 +4391,45 @@ irc_handle_nick (struct server *s, const struct irc_message *msg)
 		buffer_send (s->ctx, pm_buffer, BUFFER_LINE_NICK, 0,
 			.who    = who,
 			.object = irc_to_utf8 (s->ctx, new_nickname));
+	}
 
-		if (!lexicographically_identical)
-		{
-			// XXX: this code seems a bit ugly (but also necessary)
-			user = user_ref (user);
+	// The new nickname may collide with a user referenced by a PM buffer,
+	// or in case of data inconsistency with the server, channels.
+	// In the latter case we need the colliding user to leave all of them.
+	struct user *user_collision = NULL;
+	if (lexicographically_different
+	 && (user_collision = str_map_find (&s->irc_users, new_nickname)))
+		LIST_FOR_EACH (struct user_channel, iter, user_collision->channels)
+			irc_remove_user_from_channel (user_collision, iter->channel);
 
-			pm_buffer = irc_handle_buffer_collision
-				(s, pm_buffer, new_nickname);
+	struct buffer *buffer_collision = NULL;
+	if (lexicographically_different
+	 && (buffer_collision = str_map_find (&s->irc_buffer_map, new_nickname)))
+	{
+		hard_assert (buffer_collision->type == BUFFER_PM);
+		hard_assert (buffer_collision->user == user_collision);
 
-			user_unref (pm_buffer->user);
-			pm_buffer->user = user;
+		user_unref (buffer_collision->user);
+		buffer_collision->user = user_ref (user);
 
-			str_map_set (&s->irc_buffer_map, user->nickname, NULL);
-			str_map_set (&s->irc_buffer_map, new_nickname, pm_buffer);
-		}
+		// There's not much else we can do other than somehow try to merge
+		// one buffer into the other.  In our case, the original buffer wins.
+		buffer_merge (s->ctx, buffer_collision, pm_buffer);
+		if (s->ctx->current_buffer == pm_buffer)
+			buffer_activate (s->ctx, buffer_collision);
+		buffer_remove (s->ctx, pm_buffer);
+		pm_buffer = buffer_collision;
+	}
+
+	// The colliding user should be completely destroyed by now
+	if (lexicographically_different)
+		hard_assert (!str_map_find (&s->irc_users, new_nickname));
+
+	// Now we can rename the PM buffer to reflect the new nickname
+	if (pm_buffer)
+	{
+		str_map_set (&s->irc_buffer_map, user->nickname, NULL);
+		str_map_set (&s->irc_buffer_map, new_nickname, pm_buffer);
 
 		char *x = xstrdup_printf ("%s.%s", s->name, new_nickname);
 		buffer_rename (s->ctx, pm_buffer, x);
@@ -4464,13 +4466,9 @@ irc_handle_nick (struct server *s, const struct irc_message *msg)
 		}
 	}
 
-	// Finally rename the user
-	if (!lexicographically_identical)
-	{
-		// NOTE: this doesn't dereference anything
-		str_map_set (&s->irc_users, user->nickname, NULL);
-		str_map_set (&s->irc_users, new_nickname, user);
-	}
+	// Finally rename the user as it should be safe now
+	str_map_set (&s->irc_users, user->nickname, NULL);
+	str_map_set (&s->irc_users, new_nickname, user);
 
 	free (user->nickname);
 	user->nickname = xstrdup (new_nickname);