diff --git a/src/nasal.h b/src/nasal.h
index a324ad5..664200d 100644
--- a/src/nasal.h
+++ b/src/nasal.h
@@ -4,6 +4,7 @@
 #define __nasver__ "11.2"
 #endif
 
+#include <cstddef>
 #include <cstdint>
 
 // abbreviation of some useful basic type