diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index 73a698eec743..8a117d1c8888 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -40,7 +40,7 @@
 
 #define NHI_MAILBOX_TIMEOUT	500 /* ms */
 
-static int ring_interrupt_index(struct tb_ring *ring)
+static int ring_interrupt_index(const struct tb_ring *ring)
 {
 	int bit = ring->hop;
 	if (!ring->is_tx)