diff --git a/src/json.hpp b/src/json.hpp
index 596f7136..c312dfbb 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -9029,7 +9029,7 @@ class basic_json
         const std::streampos start_position;
 
         /// internal buffer
-        std::array<char, N> buffer;
+        std::array<char, N> buffer = {};
     };
 
     /// input adapter for buffer input