diff --git a/extras/tests/Misc/StringAdapters.cpp b/extras/tests/Misc/StringAdapters.cpp
index dbf5f06c..d8d21e46 100644
--- a/extras/tests/Misc/StringAdapters.cpp
+++ b/extras/tests/Misc/StringAdapters.cpp
@@ -5,6 +5,7 @@
 #include <Arduino.h>
 
 #include <ArduinoJson/Strings/IsString.hpp>
+#include <ArduinoJson/Strings/JsonString.hpp>
 #include <ArduinoJson/Strings/StringAdapters.hpp>
 
 #include <catch.hpp>
diff --git a/src/ArduinoJson/Strings/Adapters/JsonString.hpp b/src/ArduinoJson/Strings/Adapters/JsonString.hpp
deleted file mode 100644
index ae7e3573..00000000
--- a/src/ArduinoJson/Strings/Adapters/JsonString.hpp
+++ /dev/null
@@ -1,22 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2024, Benoit BLANCHON
-// MIT License
-
-#pragma once
-
-#include <ArduinoJson/Strings/Adapters/RamString.hpp>
-#include <ArduinoJson/Strings/JsonString.hpp>
-#include <ArduinoJson/Strings/StringAdapter.hpp>
-
-ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
-
-template <>
-struct StringAdapter<JsonString> {
-  using AdaptedString = RamString;
-
-  static const AdaptedString& adapt(const JsonString& s) {
-    return s.str_;
-  }
-};
-
-ARDUINOJSON_END_PRIVATE_NAMESPACE
diff --git a/src/ArduinoJson/Strings/JsonString.hpp b/src/ArduinoJson/Strings/JsonString.hpp
index 133067f0..abf6522c 100644
--- a/src/ArduinoJson/Strings/JsonString.hpp
+++ b/src/ArduinoJson/Strings/JsonString.hpp
@@ -4,6 +4,8 @@
 
 #pragma once
 
+#include <ArduinoJson/Strings/Adapters/RamString.hpp>
+
 #if ARDUINOJSON_ENABLE_STD_STREAM
 #  include <ostream>
 #endif
@@ -81,4 +83,15 @@ class JsonString {
   detail::RamString str_;
 };
 
+namespace detail {
+template <>
+struct StringAdapter<JsonString> {
+  using AdaptedString = RamString;
+
+  static const AdaptedString& adapt(const JsonString& s) {
+    return s.str_;
+  }
+};
+}  // namespace detail
+
 ARDUINOJSON_END_PUBLIC_NAMESPACE
diff --git a/src/ArduinoJson/Strings/StringAdapters.hpp b/src/ArduinoJson/Strings/StringAdapters.hpp
index 5da554ce..e8ff181e 100644
--- a/src/ArduinoJson/Strings/StringAdapters.hpp
+++ b/src/ArduinoJson/Strings/StringAdapters.hpp
@@ -5,7 +5,6 @@
 #pragma once
 
 #include <ArduinoJson/Polyfills/type_traits.hpp>
-#include <ArduinoJson/Strings/Adapters/JsonString.hpp>
 #include <ArduinoJson/Strings/Adapters/RamString.hpp>
 #include <ArduinoJson/Strings/Adapters/StringObject.hpp>