diff --git a/go-ogg/ogg-codec.go b/go-ogg/ogg-codec.go
index 3510f97..6b8febe 100644
--- a/go-ogg/ogg-codec.go
+++ b/go-ogg/ogg-codec.go
@@ -213,7 +213,7 @@ func (vp8 *vp8Demuxer) packet(stream *oggStream, packet []byte) (frame []byte, p
         vp8.granule = stream.currentPage.granulePos
     }
     var duration uint64 = 0
-    for i := int(vp8.pktIdx); i < len(stream.currentPage.packets); i++ {
+    if len(stream.currentPage.packets[i]) > 0 {
         duration += uint64((stream.currentPage.packets[i][0] >> 4) & 1)
     }
     vp8.lastpts = vp8.gptopts(stream.currentPage.granulePos) - duration