diff --git a/src/Mayaqua/Mayaqua.h b/src/Mayaqua/Mayaqua.h
index 63c2edc3..07b27726 100644
--- a/src/Mayaqua/Mayaqua.h
+++ b/src/Mayaqua/Mayaqua.h
@@ -8,6 +8,8 @@
 #ifndef	MAYAQUA_H
 #define	MAYAQUA_H
 
+#include <stddef.h>
+
 // PenCore.dll related
 #define	PENCORE_DLL_NAME		"|PenCore.dll"
 // #define	PENCORE_DLL_NAME_X64	"|PenCore_x64.dll" // commonized to x86