diff --git a/nsock/src/gh_heap.h b/nsock/src/gh_heap.h
index 654774a3e..9eaa2cbc2 100644
--- a/nsock/src/gh_heap.h
+++ b/nsock/src/gh_heap.h
@@ -69,6 +69,7 @@
 
 #include "error.h"
 #include <assert.h>
+#include <stddef.h>
 
 
 #if !defined(container_of)