diff --git a/sys/kern/vfs_bio.c b/sys/kern/vfs_bio.c
index b7c4d6005778..e72f5e44bf52 100644
--- a/sys/kern/vfs_bio.c
+++ b/sys/kern/vfs_bio.c
@@ -3678,7 +3678,7 @@ bufdonebio(struct bio *bip)
 	struct buf *bp;
 
 	bp = bip->bio_caller2;
-	bp->b_resid = bp->b_bcount - bip->bio_completed;
+	bp->b_resid = bip->bio_resid;
 	bp->b_ioflags = bip->bio_flags;
 	bp->b_error = bip->bio_error;
 	if (bp->b_error)