--- a/sys/vfs/hpfs/hpfs_subr.c
+++ b/sys/vfs/hpfs/hpfs_subr.c
@@ -337,7 +337,7 @@
 	dprintf(("hpfs_bmlookup: lsn: 0x%x, len 0x%lx | Step1\n", lsn, len));
 
-	if (lsn > hpmp->hpm_su.su_btotal) {
+	if (lsn >= hpmp->hpm_su.su_btotal) {
 		kprintf("hpfs_bmlookup: OUT OF VOLUME\n");
 		return ENOSPC;
 	}