diff --git a/channels/private/wrappers.hpp b/channels/private/wrappers.hpp
index 30092814..1c1859da 100644
--- a/channels/private/wrappers.hpp
+++ b/channels/private/wrappers.hpp
@@ -5,6 +5,10 @@
 *******************************************************************************/
 #ifndef _WRAPPERS_HPP_
 #define _WRAPPERS_HPP_
+
+#include <stddef.h>
+#include <stdlib.h>
+
 #ifdef MATLAB_MEX_FILE
 
 // wrapper functions if compiling from Matlab