diff --git a/sys/sys/conf.h b/sys/sys/conf.h
index 426bc2f9720e..5e173e77c099 100644
--- a/sys/sys/conf.h
+++ b/sys/sys/conf.h
@@ -61,7 +61,6 @@ struct cdev {
 #define SI_DUMPDEV	0x0080	/* is kernel dumpdev */
 #define SI_CANDELETE	0x0100	/* can do BIO_DELETE */
 #define SI_CLONELIST	0x0200	/* on a clone list */
-#define SI_ISDISK	0x0400	/* device is a disk */
 	struct timespec	si_atime;
 	struct timespec	si_ctime;
 	struct timespec	si_mtime;