diff --git a/BBGE/MT.h b/BBGE/MT.h
index 5a27dcc..0311075 100644
--- a/BBGE/MT.h
+++ b/BBGE/MT.h
@@ -1,6 +1,7 @@
 #ifndef BBGE_MT_H
 #define BBGE_MT_H
 
+#include <cstddef>
 #include <queue>
 #include <map>