diff --git a/clientapi/jsonerror/jsonerror.go b/clientapi/jsonerror/jsonerror.go
index caa216e62..97c597030 100644
--- a/clientapi/jsonerror/jsonerror.go
+++ b/clientapi/jsonerror/jsonerror.go
@@ -149,6 +149,15 @@ func MissingParam(msg string) *MatrixError {
 	return &MatrixError{"M_MISSING_PARAM", msg}
 }
 
+// LeaveServerNoticeError is an error returned when trying to reject an invite
+// for a server notice room.
+func LeaveServerNoticeError() *MatrixError {
+	return &MatrixError{
+		ErrCode: "M_CANNOT_LEAVE_SERVER_NOTICE_ROOM",
+		Err:     "You cannot reject this invite",
+	}
+}
+
 type IncompatibleRoomVersionError struct {
 	RoomVersion string `json:"room_version"`
 	Error       string `json:"error"`
diff --git a/clientapi/routing/leaveroom.go b/clientapi/routing/leaveroom.go
index f40b4d85a..a34dd02d3 100644
--- a/clientapi/routing/leaveroom.go
+++ b/clientapi/routing/leaveroom.go
@@ -41,7 +41,7 @@ func LeaveRoomByID(
 		if leaveRes.Code != 0 {
 			return util.JSONResponse{
 				Code: leaveRes.Code,
-				JSON: jsonerror.Forbidden(leaveRes.Message),
+				JSON: jsonerror.LeaveServerNoticeError(),
 			}
 		}
 		return util.JSONResponse{