diff --git a/tdtl/td/tl/tl_writer.cpp b/tdtl/td/tl/tl_writer.cpp
index 8d656a996..5e80315aa 100644
--- a/tdtl/td/tl/tl_writer.cpp
+++ b/tdtl/td/tl/tl_writer.cpp
@@ -16,7 +16,7 @@ namespace tl {
 
 std::string TL_writer::int_to_string(int x) {
   char buf[15];
-  std::sprintf(buf, "%d", x);
+  std::snprintf(buf, sizeof(buf), "%d", x);
   return buf;
 }