diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index 19bc8c923..c08518258 100755
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -3755,7 +3755,7 @@ static long st_ioctl_common(struct file *file, unsigned int cmd_in, void __user
 		    ((STp->density << MT_ST_DENSITY_SHIFT) & MT_ST_DENSITY_MASK);
 		mt_status.mt_blkno = STps->drv_block;
 		mt_status.mt_fileno = STps->drv_file;
-		if (STp->block_size != 0) {
+		if (STp->block_size != 0 && mt_status.mt_blkno >= 0) {
 			if (STps->rw == ST_WRITING)
 				mt_status.mt_blkno +=
 				    (STp->buffer)->buffer_bytes / STp->block_size;