--- sudo-1.8.25p1.old/include/sudo_compat.h
+++ sudo-1.8.25p1/include/sudo_compat.h
@@ -34,6 +34,8 @@
 # endif /* HAVE_STRING_H */
 #endif /* HAVE_MEMSET_S && rsize_t */
 
+#include <sys/types.h> /* for id_t */
+
 /*
  * Macros and functions that may be missing on some operating systems.
  */