diff --git a/td/telegram/net/MtprotoHeader.h b/td/telegram/net/MtprotoHeader.h
index 34d22c4a3..2dae30972 100644
--- a/td/telegram/net/MtprotoHeader.h
+++ b/td/telegram/net/MtprotoHeader.h
@@ -9,6 +9,7 @@
 #include "td/telegram/net/Proxy.h"
 
 #include "td/utils/common.h"
+#include "td/utils/port/RwMutex.h"
 #include "td/utils/Slice.h"
 
 namespace td {
@@ -30,15 +31,18 @@ class MtprotoHeader {
   };
 
   explicit MtprotoHeader(const Options &options) : options_(options) {
-    gen_headers();
+    default_header_ = gen_header(options_, false);
+    anonymous_header_ = gen_header(options_, true);
   }
 
   void set_proxy(Proxy proxy) {
+    auto lock = rw_mutex_.lock_write();
     options_.proxy = std::move(proxy);
     default_header_ = gen_header(options_, false);
   }
 
   bool set_parameters(string parameters) {
+    auto lock = rw_mutex_.lock_write();
     if (options_.parameters == parameters) {
       return false;
     }
@@ -49,6 +53,7 @@ class MtprotoHeader {
   }
 
   bool set_is_emulator(bool is_emulator) {
+    auto lock = rw_mutex_.lock_write();
     if (options_.is_emulator == is_emulator) {
       return false;
     }
@@ -59,6 +64,7 @@ class MtprotoHeader {
   }
 
   bool set_language_pack(string language_pack) {
+    auto lock = rw_mutex_.lock_write();
     if (options_.language_pack == language_pack) {
       return false;
     }
@@ -69,6 +75,7 @@ class MtprotoHeader {
   }
 
   bool set_language_code(string language_code) {
+    auto lock = rw_mutex_.lock_write();
     if (options_.language_code == language_code) {
       return false;
     }
@@ -79,6 +86,7 @@ class MtprotoHeader {
   }
 
   bool set_tz_offset(int32 tz_offset) {
+    auto lock = rw_mutex_.lock_write();
     if (options_.tz_offset == tz_offset) {
       return false;
     }
@@ -88,14 +96,18 @@ class MtprotoHeader {
     return true;
   }
 
-  Slice get_default_header() const {
+  string get_default_header() const {
+    auto lock = rw_mutex_.lock_read();
     return default_header_;
   }
-  Slice get_anonymous_header() const {
+
+  string get_anonymous_header() const {
+    auto lock = rw_mutex_.lock_read();
     return anonymous_header_;
   }
 
   string get_system_language_code() const {
+    auto lock = rw_mutex_.lock_read();
     return options_.system_language_code;
   }
 
@@ -103,11 +115,7 @@ class MtprotoHeader {
   Options options_;
   string default_header_;
   string anonymous_header_;
-
-  void gen_headers() {
-    default_header_ = gen_header(options_, false);
-    anonymous_header_ = gen_header(options_, true);
-  }
+  mutable RwMutex rw_mutex_;
 
   static string gen_header(const Options &options, bool is_anonymous);
 };
diff --git a/td/telegram/net/Session.cpp b/td/telegram/net/Session.cpp
index 5e4b6b3d2..c6b587182 100644
--- a/td/telegram/net/Session.cpp
+++ b/td/telegram/net/Session.cpp
@@ -278,9 +278,9 @@ Session::Session(unique_ptr<Callback> callback, std::shared_ptr<AuthDataShared>
   long_poll_connection_.connection_id_ = 1;
 
   if (is_cdn) {
-    auth_data_.set_header(G()->mtproto_header().get_anonymous_header().str());
+    auth_data_.set_header(G()->mtproto_header().get_anonymous_header());
   } else {
-    auth_data_.set_header(G()->mtproto_header().get_default_header().str());
+    auth_data_.set_header(G()->mtproto_header().get_default_header());
   }
   last_activity_timestamp_ = now;
   last_success_timestamp_ = now - 366 * 86400;