--- ./include/sudo_compat.h.orig
+++ ./include/sudo_compat.h
@@ -25,6 +25,7 @@
 #endif
 #if !defined(HAVE_MEMSET_S) && !defined(rsize_t)
 # include <stddef.h>	/* for rsize_t */
+#include <sys/types.h> /* for id_t */
 # ifdef HAVE_STRING_H
 #  include <string.h>	/* for rsize_t on AIX */
 # endif /* HAVE_STRING_H */