diff --git a/src/jansson_private.h b/src/jansson_private.h
index 4490702a..6d7e46cc 100644
--- a/src/jansson_private.h
+++ b/src/jansson_private.h
@@ -8,11 +8,12 @@
 #ifndef JANSSON_PRIVATE_H
 #define JANSSON_PRIVATE_H
 
+#include <stddef.h>
 #include "jansson.h"
 #include "hashtable.h"
 
 #define container_of(ptr_, type_, member_)  \
-    ((type_ *)((char *)ptr_ - (size_t)&((type_ *)0)->member_))
+    ((type_ *)((char *)ptr_ - offsetof(type_, member_)))
 
 typedef struct {
     json_t json;