diff --git a/include/nlohmann/detail/output/serializer.hpp b/include/nlohmann/detail/output/serializer.hpp
index 0a34c8011..9e3f75660 100644
--- a/include/nlohmann/detail/output/serializer.hpp
+++ b/include/nlohmann/detail/output/serializer.hpp
@@ -497,7 +497,7 @@ class serializer
                     {
                         case error_handler_t::strict:
                         {
-                            std::string sn(3, '\0');
+                            std::string sn(8, '\0');
                             (std::snprintf)(&sn[0], sn.size(), "%.2X", byte);
                             JSON_THROW(type_error::create(316, "invalid UTF-8 byte at index " + std::to_string(i) + ": 0x" + sn));
                         }
@@ -591,7 +591,7 @@ class serializer
             {
                 case error_handler_t::strict:
                 {
-                    std::string sn(3, '\0');
+                    std::string sn(8, '\0');
                     (std::snprintf)(&sn[0], sn.size(), "%.2X", static_cast<std::uint8_t>(s.back()));
                     JSON_THROW(type_error::create(316, "incomplete UTF-8 string; last byte: 0x" + sn));
                 }
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 492118a5f..32865fd8e 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -16052,7 +16052,7 @@ class serializer
                     {
                         case error_handler_t::strict:
                         {
-                            std::string sn(3, '\0');
+                            std::string sn(8, '\0');
                             (std::snprintf)(&sn[0], sn.size(), "%.2X", byte);
                             JSON_THROW(type_error::create(316, "invalid UTF-8 byte at index " + std::to_string(i) + ": 0x" + sn));
                         }
@@ -16146,7 +16146,7 @@ class serializer
             {
                 case error_handler_t::strict:
                 {
-                    std::string sn(3, '\0');
+                    std::string sn(8, '\0');
                     (std::snprintf)(&sn[0], sn.size(), "%.2X", static_cast<std::uint8_t>(s.back()));
                     JSON_THROW(type_error::create(316, "incomplete UTF-8 string; last byte: 0x" + sn));
                 }