diff --git a/example/main.go b/example/main.go
index 8875e14..87f9eba 100644
--- a/example/main.go
+++ b/example/main.go
@@ -12,8 +12,9 @@ import (
 
 func usage(w io.Writer) {
 	io.WriteString(w, `
-sayhello: start to display oneline log per second
-bye: quit
+setprompt <prompt>
+say <hello>
+bye
 `[1:])
 }
 
@@ -22,6 +23,7 @@ var completer = readline.NewPrefixCompleter(
 		readline.PcItem("hello"),
 		readline.PcItem("bye"),
 	),
+	readline.PcItem("setprompt"),
 	readline.PcItem("bye"),
 	readline.PcItem("help"),
 	readline.PcItem("go",
@@ -52,6 +54,13 @@ func main() {
 		switch {
 		case line == "help":
 			usage(l.Stderr())
+		case strings.HasPrefix(line, "setprompt"):
+			prompt := line[10:]
+			if prompt == "" {
+				log.Println("setprompt <prompt>")
+				break
+			}
+			l.SetPrompt(prompt)
 		case strings.HasPrefix(line, "say"):
 			line := strings.TrimSpace(line[3:])
 			if len(line) == 0 {
diff --git a/operation.go b/operation.go
index 85251a2..dc2cd02 100644
--- a/operation.go
+++ b/operation.go
@@ -49,6 +49,10 @@ func NewOperation(t *Terminal, cfg *Config) *Operation {
 	return op
 }
 
+func (o *Operation) SetPrompt(s string) {
+	o.buf.SetPrompt(s)
+}
+
 func (o *Operation) ioloop() {
 	for {
 		keepInSearchMode := false
diff --git a/readline.go b/readline.go
index 76a25d4..e4032ad 100644
--- a/readline.go
+++ b/readline.go
@@ -50,6 +50,10 @@ func New(prompt string) (*Instance, error) {
 	return NewEx(&Config{Prompt: prompt})
 }
 
+func (i *Instance) SetPrompt(s string) {
+	i.o.SetPrompt(s)
+}
+
 func (i *Instance) Stdout() io.Writer {
 	return i.o.Stdout()
 }
diff --git a/runebuf.go b/runebuf.go
index 41607ed..724d6ef 100644
--- a/runebuf.go
+++ b/runebuf.go
@@ -16,12 +16,16 @@ type RuneBuffer struct {
 
 func NewRuneBuffer(w io.Writer, prompt string) *RuneBuffer {
 	rb := &RuneBuffer{
-		prompt: []rune(prompt),
-		w:      w,
+		w: w,
 	}
+	rb.SetPrompt(prompt)
 	return rb
 }
 
+func (r *RuneBuffer) SetPrompt(prompt string) {
+	r.prompt = []rune(prompt)
+}
+
 func (r *RuneBuffer) CurrentWidth(x int) int {
 	return RunesWidth(r.buf[:x])
 }