diff --git a/.changeset/wet-guests-eat.md b/.changeset/wet-guests-eat.md
new file mode 100644
index 00000000..7f4bfa47
--- /dev/null
+++ b/.changeset/wet-guests-eat.md
@@ -0,0 +1,5 @@
+---
+"github.com/livekit/protocol": patch
+---
+
+Validate SipCallTo in CreateSIPParticipantRequest.
diff --git a/livekit/sip.go b/livekit/sip.go
index d7ce71c5..e91db6bb 100644
--- a/livekit/sip.go
+++ b/livekit/sip.go
@@ -182,6 +182,8 @@ func (p *CreateSIPParticipantRequest) Validate() error {
 	}
 	if p.SipCallTo == "" {
 		return errors.New("missing sip callee number")
+	} else if strings.Contains(p.SipCallTo, "@") {
+		return errors.New("SipCallTo should be a phone number or SIP user, not a full SIP URI")
 	}
 	if p.RoomName == "" {
 		return errors.New("missing room name")