diff --git a/demux/codec_tags.c b/demux/codec_tags.c
index d111c39ae3..ea6c8fe19d 100644
--- a/demux/codec_tags.c
+++ b/demux/codec_tags.c
@@ -75,7 +75,7 @@ static void map_audio_pcm_tag(struct mp_codec_params *c)
 
         // Compressed formats might use this.
         c->extradata += 22;
-        c->extradata_size += 22;
+        c->extradata_size -= 22;
     }
 
     int bits = c->bits_per_coded_sample;