diff --git a/libavcodec/gsmdec.c b/libavcodec/gsmdec.c
index c169112311..e3c87af513 100644
--- a/libavcodec/gsmdec.c
+++ b/libavcodec/gsmdec.c
@@ -34,8 +34,8 @@
 
 static av_cold int gsm_init(AVCodecContext *avctx)
 {
-    avctx->channels       = 1;
-    avctx->channel_layout = AV_CH_LAYOUT_MONO;
+    av_channel_layout_uninit(&avctx->ch_layout);
+    avctx->ch_layout      = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
     if (!avctx->sample_rate)
         avctx->sample_rate = 8000;
     avctx->sample_fmt     = AV_SAMPLE_FMT_S16;