diff --git a/audio/vorbis/decode.go b/audio/vorbis/decode.go
index 364f0203b..19213d2f9 100644
--- a/audio/vorbis/decode.go
+++ b/audio/vorbis/decode.go
@@ -32,6 +32,8 @@ func (s *Stream) Read(p []byte) (int, error) {
 }
 
 // Seek is implementation of io.Seeker's Seek.
+//
+// Note that Seek can take long since decoding is a relatively heavy task.
 func (s *Stream) Seek(offset int64, whence int) (int64, error) {
 	return s.decoded.Seek(offset, whence)
 }