diff --git a/include/cstd.h b/include/cstd.h
index 707f74157..0ffe6c3d5 100644
--- a/include/cstd.h
+++ b/include/cstd.h
@@ -50,6 +50,7 @@
  *
  */
 
+#include <stddef.h>
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>