diff --git a/sound/soc/codecs/rt5640.c b/sound/soc/codecs/rt5640.c
index c26a8f8..2f6bb16 100644
--- a/sound/soc/codecs/rt5640.c
+++ b/sound/soc/codecs/rt5640.c
@@ -926,7 +926,7 @@
 	return 0;
 }
 
-void hp_amp_power_on(struct snd_soc_codec *codec)
+static void hp_amp_power_on(struct snd_soc_codec *codec)
 {
 	struct rt5640_priv *rt5640 = snd_soc_codec_get_drvdata(codec);