diff --git a/cmd/signaldctl/cmd/account/register/register-account.go b/cmd/signaldctl/cmd/account/register/register-account.go
index f97504d..b2c92c0 100644
--- a/cmd/signaldctl/cmd/account/register/register-account.go
+++ b/cmd/signaldctl/cmd/account/register/register-account.go
@@ -26,7 +26,8 @@ import (
 )
 
 var (
-	voice bool
+	voice   bool
+	captcha string
 
 	RegisterAccountCmd = &cobra.Command{
 		Use:   "register [phone number]",
@@ -44,6 +45,7 @@ var (
 				ID:       requestID,
 				Username: args[0],
 				Voice:    voice,
+				Captcha:  captcha,
 			})
 			if err != nil {
 				log.Fatal("error sending request to signald: ", err)
@@ -51,9 +53,12 @@ var (
 			c := make(chan v0.LegacyResponse)
 			go common.Signald.Listen(c)
 			response := signald.GetLegacyResponse(c, requestID)
-			if response.Type == "verification_required" {
+			switch response.Type {
+			case "verification_required":
 				log.Println("verification code requested. submit with: signaldctl account verify", args[0], "<code>")
-			} else {
+			case "captcha_required":
+				log.Println("captcha required. Please provide a captcha token with the --captcha argument (see https://gitlab.com/signald/signald/-/wikis/Captchas)")
+			default:
 				log.Fatalf("unexpected response from signald when requesting verification code: %+v", response)
 			}
 		},
@@ -62,4 +67,5 @@ var (
 
 func init() {
 	RegisterAccountCmd.Flags().BoolVarP(&voice, "voice", "V", false, "request verification code be sent via an automated voice call (code is sent via SMS by default)")
+	RegisterAccountCmd.Flags().StringVarP(&captcha, "captcha", "c", "", "a captcha token may be required to register, see https://gitlab.com/signald/signald/-/wikis/Captchas for how to get one")
 }
diff --git a/signald/client-protocol/v0/signaldrequest.go b/signald/client-protocol/v0/signaldrequest.go
index d087387..a695cd3 100644
--- a/signald/client-protocol/v0/signaldrequest.go
+++ b/signald/client-protocol/v0/signaldrequest.go
@@ -21,7 +21,7 @@ type LegacyRequest struct {
 	ID                  string           `json:"id,omitempty"`
 	Username            string           `json:"username,omitempty"`
 	MessageBody         string           `json:"messageBody,omitempty"`
-	RecipientAddress    JsonAddress      `json:"recipientAddress,omitempty"`
+	RecipientAddress    *JsonAddress     `json:"recipientAddress,omitempty"`
 	RecipientGroupID    string           `json:"recipientGroupId,omitempty"`
 	Voice               bool             `json:"voice,omitempty"`
 	Code                string           `json:"code,omitempty"`
@@ -32,6 +32,7 @@ type LegacyRequest struct {
 	GroupName           string           `json:"groupName,omitempty"`
 	Members             []string         `json:"members,omitempty"`
 	Avatar              string           `json:"avatar,omitempty"`
+	Captcha             string           `json:"captcha,omitempty"`
 }
 
 type JsonAddress struct {