diff --git a/core/src/vmath.h b/core/src/vmath.h
index 5877129..9b2aed2 100644
--- a/core/src/vmath.h
+++ b/core/src/vmath.h
@@ -1,6 +1,7 @@
 #ifndef _fencer_vmath_h
 #define _fencer_vmath_h
 
+#include "stddef.h"
 #include <math.h>
 
 #if VMATH_SDL == 1