diff --git a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/offline/DashDownloader.java b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/offline/DashDownloader.java
index abae7a5f1e..4a90feb532 100644
--- a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/offline/DashDownloader.java
+++ b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/offline/DashDownloader.java
@@ -117,7 +117,8 @@ public final class DashDownloader extends SegmentDownloader<DashManifest, Repres
         }
       }
 
-      int segmentCount = index.getSegmentCount(C.TIME_UNSET);
+      long periodDurationUs = manifest.getPeriodDurationUs(key.periodIndex);
+      int segmentCount = index.getSegmentCount(periodDurationUs);
       if (segmentCount == DashSegmentIndex.INDEX_UNBOUNDED) {
         throw new DownloadException("Unbounded index for representation: " + key);
       }