--- a/sys/dev/sound/pci/hda/hdac.c
+++ b/sys/dev/sound/pci/hda/hdac.c
@@ -1931,7 +1931,7 @@ hdac_stream_alloc(device_t dev, device_t child, int dir, int format, int stripe,
 	/* Allocate stream number */
 	if (ss >= sc->num_iss + sc->num_oss)
-		stream = 15 - (ss - sc->num_iss + sc->num_oss);
+		stream = 15 - (ss - sc->num_iss - sc->num_oss);
 	else if (ss >= sc->num_iss)
 		stream = ss - sc->num_iss + 1;
 	else