diff --git a/td/telegram/ClientJson.cpp b/td/telegram/ClientJson.cpp
index 94358660c..71d424252 100644
--- a/td/telegram/ClientJson.cpp
+++ b/td/telegram/ClientJson.cpp
@@ -67,10 +67,10 @@ static std::string from_response(const td_api::Object &object, const string &ext
 
 static TD_THREAD_LOCAL std::string *current_output;
 
-static CSlice store_string(std::string str) {
+static const char *store_string(std::string str) {
   init_thread_local<std::string>(current_output);
   *current_output = std::move(str);
-  return *current_output;
+  return current_output->c_str();
 }
 
 void ClientJson::send(Slice request) {
@@ -83,10 +83,10 @@ void ClientJson::send(Slice request) {
   client_.send(Client::Request{extra_id, std::move(parsed_request.first)});
 }
 
-CSlice ClientJson::receive(double timeout) {
+const char *ClientJson::receive(double timeout) {
   auto response = client_.receive(timeout);
   if (!response.object) {
-    return {};
+    return nullptr;
   }
 
   std::string extra;
@@ -101,7 +101,7 @@ CSlice ClientJson::receive(double timeout) {
   return store_string(from_response(*response.object, extra));
 }
 
-CSlice ClientJson::execute(Slice request) {
+const char *ClientJson::execute(Slice request) {
   auto parsed_request = to_request(request);
   return store_string(from_response(*Client::execute(Client::Request{0, std::move(parsed_request.first)}).object,
                                     parsed_request.second));
diff --git a/td/telegram/ClientJson.h b/td/telegram/ClientJson.h
index 3b08cd28b..62df510b7 100644
--- a/td/telegram/ClientJson.h
+++ b/td/telegram/ClientJson.h
@@ -22,9 +22,9 @@ class ClientJson final {
  public:
   void send(Slice request);
 
-  CSlice receive(double timeout);
+  const char *receive(double timeout);
 
-  static CSlice execute(Slice request);
+  static const char *execute(Slice request);
 
  private:
   Client client_;
diff --git a/td/telegram/td_json_client.cpp b/td/telegram/td_json_client.cpp
index 8637ee2e6..33d29d4b0 100644
--- a/td/telegram/td_json_client.cpp
+++ b/td/telegram/td_json_client.cpp
@@ -27,19 +27,9 @@ void td_json_client_send(void *client, const char *request) {
 }
 
 const char *td_json_client_receive(void *client, double timeout) {
-  auto slice = static_cast<td::ClientJson *>(client)->receive(timeout);
-  if (slice.empty()) {
-    return nullptr;
-  } else {
-    return slice.c_str();
-  }
+  return static_cast<td::ClientJson *>(client)->receive(timeout);
 }
 
 const char *td_json_client_execute(void *client, const char *request) {
-  auto slice = td::ClientJson::execute(td::Slice(request == nullptr ? "" : request));
-  if (slice.empty()) {
-    return nullptr;
-  } else {
-    return slice.c_str();
-  }
+  return td::ClientJson::execute(td::Slice(request == nullptr ? "" : request));
 }
diff --git a/td/telegram/td_json_client.h b/td/telegram/td_json_client.h
index 2d030ecdb..d713c532c 100644
--- a/td/telegram/td_json_client.h
+++ b/td/telegram/td_json_client.h
@@ -84,7 +84,7 @@ TDJSON_EXPORT const char *td_json_client_receive(void *client, double timeout);
  * in the same thread, so it can't be used after that.
  * \param[in] client The client. Currently ignored for all requests, so NULL can be passed.
  * \param[in] request JSON-serialized null-terminated request to TDLib.
- * \return JSON-serialized null-terminated request response. May be NULL if the request can't be parsed.
+ * \return JSON-serialized null-terminated request response.
  */
 TDJSON_EXPORT const char *td_json_client_execute(void *client, const char *request);