diff --git a/include/nlohmann/detail/conversions/to_json.hpp b/include/nlohmann/detail/conversions/to_json.hpp
index 960d92e20..a0ca4211a 100644
--- a/include/nlohmann/detail/conversions/to_json.hpp
+++ b/include/nlohmann/detail/conversions/to_json.hpp
@@ -238,7 +238,7 @@ void to_json(BasicJsonType& j, const CompatibleString& s)
 {
     if (!j.is_null())
     {
-        j = nullptr;
+        j = BasicJsonType();
     }
     external_constructor<value_t::string>::construct(j, s);
 }
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index 219a6a480..4bdadd871 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -4696,7 +4696,7 @@ void to_json(BasicJsonType& j, const CompatibleString& s)
 {
     if (!j.is_null())
     {
-        j = nullptr;
+        j = BasicJsonType();
     }
     external_constructor<value_t::string>::construct(j, s);
 }