diff --git a/reactos/lib/inflib/inflib.h b/reactos/lib/inflib/inflib.h
index b4a085477df..7dff17fa035 100644
--- a/reactos/lib/inflib/inflib.h
+++ b/reactos/lib/inflib/inflib.h
@@ -5,6 +5,7 @@
  */
 
 #include <ctype.h>
+#include <stddef.h>
 #include <stdlib.h>
 
 #include "builddep.h"