diff --git a/sound/core/oss/pcm_plugin.h b/sound/core/oss/pcm_plugin.h
index 38e2c14cb893..73c068abaca5 100644
--- a/sound/core/oss/pcm_plugin.h
+++ b/sound/core/oss/pcm_plugin.h
@@ -172,7 +172,7 @@ snd_pcm_sframes_t snd_pcm_oss_readv3(struct snd_pcm_substream *substream,
 
 static inline snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *handle, snd_pcm_uframes_t drv_size) { return drv_size; }
 static inline snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *handle, snd_pcm_uframes_t clt_size) { return clt_size; }
-static inline int snd_pcm_plug_slave_format(int format, struct snd_mask *format_mask) { return format; }
+static inline int snd_pcm_plug_slave_format(int format, const struct snd_mask *format_mask) { return format; }
 
 #endif