diff --git a/src/ArduinoJson/Memory/StringNode.hpp b/src/ArduinoJson/Memory/StringNode.hpp
index 3f020d97..06dcba09 100644
--- a/src/ArduinoJson/Memory/StringNode.hpp
+++ b/src/ArduinoJson/Memory/StringNode.hpp
@@ -8,6 +8,7 @@
 #include <ArduinoJson/Namespace.hpp>
 #include <ArduinoJson/Polyfills/assert.hpp>
 
+#include <stddef.h>  // offsetof
 #include <stdint.h>  // uint16_t
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE