diff --git a/td/generate/tl_writer_cpp.cpp b/td/generate/tl_writer_cpp.cpp
index bfaeb2eb..f9c5029a 100644
--- a/td/generate/tl_writer_cpp.cpp
+++ b/td/generate/tl_writer_cpp.cpp
@@ -32,7 +32,7 @@ std::string TD_TL_writer_cpp::gen_output_begin() const {
          "std::string to_string(const BaseObject &value) {\n"
          "  TlStorerToString storer;\n"
          "  value.store(storer, \"\");\n"
-         "  return storer.str();\n"
+         "  return storer.move_as_str();\n"
          "}\n";
 }
 
diff --git a/tdutils/td/utils/tl_storers.h b/tdutils/td/utils/tl_storers.h
index f4c6d614..4476115b 100644
--- a/tdutils/td/utils/tl_storers.h
+++ b/tdutils/td/utils/tl_storers.h
@@ -142,12 +142,10 @@ class TlStorerCalcLength {
 
 class TlStorerToString {
   std::string result;
-  int shift = 0;
+  size_t shift = 0;
 
   void store_field_begin(const char *name) {
-    for (int i = 0; i < shift; i++) {
-      result += ' ';
-    }
+    result.append(shift, ' ');
     if (name && name[0]) {
       result += name;
       result += " = ";
@@ -155,7 +153,7 @@ class TlStorerToString {
   }
 
   void store_field_end() {
-    result += "\n";
+    result += '\n';
   }
 
   void store_long(int64 value) {
@@ -165,14 +163,14 @@ class TlStorerToString {
   void store_binary(Slice data) {
     static const char *hex = "0123456789ABCDEF";
 
-    result.append("{ ");
+    result.append("{ ", 2);
     for (auto c : data) {
       unsigned char byte = c;
       result += hex[byte >> 4];
       result += hex[byte & 15];
       result += ' ';
     }
-    result.append("}");
+    result += '}';
   }
 
  public:
@@ -211,7 +209,7 @@ class TlStorerToString {
   void store_field(const char *name, const string &value) {
     store_field_begin(name);
     result += '"';
-    result.append(value.data(), value.size());
+    result += value;
     result += '"';
     store_field_end();
   }
@@ -265,16 +263,14 @@ class TlStorerToString {
   }
 
   void store_class_end() {
+    CHECK(shift >= 2);
     shift -= 2;
-    for (int i = 0; i < shift; i++) {
-      result += ' ';
-    }
+    result.append(shift, ' ');
     result += "}\n";
-    CHECK(shift >= 0);
   }
 
-  std::string str() const {
-    return result;
+  std::string move_as_str() {
+    return std::move(result);
   }
 };