diff --git a/td/telegram/MessageContentType.h b/td/telegram/MessageContentType.h
index 954a5a67c834..a01b9d3ea765 100644
--- a/td/telegram/MessageContentType.h
+++ b/td/telegram/MessageContentType.h
@@ -70,4 +70,10 @@ bool is_service_message_content(MessageContentType content_type);
 
 bool can_have_message_content_caption(MessageContentType content_type);
 
+struct MessageContentTypeHash {
+  std::size_t operator()(MessageContentType content_type) const {
+    return std::hash<int32>()(static_cast<int32>(content_type));
+  }
+};
+
 }  // namespace td
diff --git a/td/telegram/MessagesManager.cpp b/td/telegram/MessagesManager.cpp
index d9b41d58b6a9..634f2a344771 100644
--- a/td/telegram/MessagesManager.cpp
+++ b/td/telegram/MessagesManager.cpp
@@ -22961,7 +22961,7 @@ Result<vector<MessageId>> MessagesManager::send_message_group(
   TRY_RESULT(message_send_options, process_message_send_options(dialog_id, std::move(options)));
 
   vector<std::pair<unique_ptr<MessageContent>, int32>> message_contents;
-  std::unordered_set<MessageContentType> message_content_types;
+  std::unordered_set<MessageContentType, MessageContentTypeHash> message_content_types;
   for (auto &input_message_content : input_message_contents) {
     TRY_RESULT(message_content, process_input_message_content(dialog_id, std::move(input_message_content)));
     TRY_STATUS(can_use_message_send_options(message_send_options, message_content));