diff --git a/mcu.c b/mcu.c
index c78b527b..a2df0c2b 100644
--- a/mcu.c
+++ b/mcu.c
@@ -267,7 +267,8 @@ error:
 	return -ENOENT;
 }
 
-int mt76_mcu_function_select(struct mt76_dev *dev, enum mcu_function func, u32 val)
+static int
+mt76_mcu_function_select(struct mt76_dev *dev, enum mcu_function func, u32 val)
 {
 	struct sk_buff *skb;
 	struct {