diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index b24bf9bcbe2d..ecd27a6fc7f9 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -2035,7 +2035,7 @@ static unsigned int comedi_poll(struct file *file, poll_table *wait)
 
 	s = comedi_write_subdevice(dev, minor);
 	if (s && s->async) {
-		unsigned int bps = bytes_per_sample(s->async->subdevice);
+		unsigned int bps = bytes_per_sample(s);
 
 		poll_wait(file, &s->async->wait_head, wait);
 		comedi_buf_write_alloc(s->async, s->async->prealloc_bufsz);