diff --git a/include/SFML/System/Resource.hpp b/include/SFML/System/Resource.hpp
index 236adeb57..ac9a170ca 100644
--- a/include/SFML/System/Resource.hpp
+++ b/include/SFML/System/Resource.hpp
@@ -31,6 +31,7 @@
 #include <SFML/System/Lock.hpp>
 #include <SFML/System/Mutex.hpp>
 #include <set>
+#include <cstddef>
 
 
 namespace sf