diff --git a/symphonia-format-isomp4/src/demuxer.rs b/symphonia-format-isomp4/src/demuxer.rs
index 7082edb8..aa728542 100644
--- a/symphonia-format-isomp4/src/demuxer.rs
+++ b/symphonia-format-isomp4/src/demuxer.rs
@@ -235,7 +235,11 @@ impl<'s> IsoMp4Reader<'s> {
         }
 
         // Instantiate a `TrackState` for each track in the media.
-        let track_states = (0..moov.traks.len()).map(TrackState::new).collect::<Vec<TrackState>>();
+        let track_states = moov
+            .traks
+            .iter()
+            .map(|trak| TrackState::new(trak.tkhd.id as usize))
+            .collect::<Vec<TrackState>>();
 
         // Instantiate a `Track` for all track states above.
         let tracks = track_states