diff --git a/td/telegram/ContactsManager.cpp b/td/telegram/ContactsManager.cpp
index 6c8ee4497..28f113af1 100644
--- a/td/telegram/ContactsManager.cpp
+++ b/td/telegram/ContactsManager.cpp
@@ -6210,6 +6210,9 @@ void ContactsManager::check_dialog_username(DialogId dialog_id, const string &us
         return promise.set_value(CheckDialogUsernameResult::Invalid);
       }
       if (error.message() == "USERNAME_PURCHASE_AVAILABLE") {
+        if (begins_with(G()->get_option_string("my_phone_number"), "1")) {
+          return promise.set_value(CheckDialogUsernameResult::Invalid);
+        }
         return promise.set_value(CheckDialogUsernameResult::Purchasable);
       }
       return promise.set_error(std::move(error));