diff --git a/src/api/api.go b/src/api/api.go
index adbb353..c5d205d 100644
--- a/src/api/api.go
+++ b/src/api/api.go
@@ -31,6 +31,7 @@ type GroupEntry struct {
 
 type RegisterNumberRequest struct {
 	UseVoice bool `json:"use_voice"`
+	Captcha string `json:"captcha"`
 }
 
 type VerifyNumberSettings struct {
@@ -328,6 +329,7 @@ func (a *Api) RegisterNumber(c *gin.Context) {
 		}
 	} else {
 		req.UseVoice = false
+		req.Captcha = ""
 	}
 
 	if number == "" {
@@ -341,6 +343,10 @@ func (a *Api) RegisterNumber(c *gin.Context) {
 		command = append(command, "--voice")
 	}
 
+	if req.Captcha != "" {
+		command = append(command, []string{"--captcha", req.Captcha}...)
+	}
+
 	_, err := runSignalCli(true, command, "")
 	if err != nil {
 		c.JSON(400, gin.H{"error": err.Error()})