diff --git a/libavcodec/encode.c b/libavcodec/encode.c
index a436be2657..8ca07814ee 100644
--- a/libavcodec/encode.c
+++ b/libavcodec/encode.c
@@ -736,6 +736,8 @@ static int encode_preinit_audio(AVCodecContext *avctx)
         }
     }
 
+    if (!avctx->bits_per_raw_sample)
+        avctx->bits_per_raw_sample = av_get_exact_bits_per_sample(avctx->codec_id);
     if (!avctx->bits_per_raw_sample)
         avctx->bits_per_raw_sample = 8 * av_get_bytes_per_sample(avctx->sample_fmt);