diff --git a/libmpdemux/demux_audio.c b/libmpdemux/demux_audio.c
index fa86b1d242..58ec382c7f 100644
--- a/libmpdemux/demux_audio.c
+++ b/libmpdemux/demux_audio.c
@@ -229,6 +229,8 @@ get_flac_metadata (demuxer_t* demuxer)
           ptr += 4;
 
           comment = ptr;
+          if (&comment[length] < comments || &comment[length] >= &comments[blk_len])
+            return;
           c = comment[length];
           comment[length] = 0;