diff --git a/client/connection.go b/client/connection.go
index 9c7676e..0b3f3ad 100644
--- a/client/connection.go
+++ b/client/connection.go
@@ -20,6 +20,9 @@ type Conn struct {
 	Me      *state.Nick
 	Network string
 
+	// Replaceable function to customise the 433 handler's new nick
+	NewNick func(string) string
+
 	// Event handler registry and dispatcher
 	ER event.EventRegistry
 	ED event.EventDispatcher
@@ -97,6 +100,7 @@ func Client(nick, ident, name string,
 		SSLConfig: nil,
 		PingFreq:  3 * time.Minute,
 		Flood:     false,
+		NewNick:   func(s string) string { return s + "_" },
 		badness:   0,
 		lastsent:  time.Now(),
 	}
diff --git a/client/handlers.go b/client/handlers.go
index 2624a71..72a72c6 100644
--- a/client/handlers.go
+++ b/client/handlers.go
@@ -79,7 +79,7 @@ func (conn *Conn) h_001(line *Line) {
 // Handler to deal with "433 :Nickname already in use"
 func (conn *Conn) h_433(line *Line) {
 	// Args[1] is the new nick we were attempting to acquire
-	neu := line.Args[1] + "_"
+	neu := conn.NewNick(line.Args[1])
 	conn.Nick(neu)
 	// if this is happening before we're properly connected (i.e. the nick
 	// we sent in the initial NICK command is in use) we will not receive