diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
index 4e8cccaa23..72ecd2c767 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java
@@ -709,6 +709,7 @@ public class ConcatenatingMediaSource extends CompositeMediaSource<MediaSourceHo
       //     unlikely to be a problem as a non-zero default position usually only occurs for live
       //     playbacks and seeking to zero in a live window would cause BehindLiveWindowExceptions
       //     anyway.
+      timeline.getWindow(/* windowIndex= */ 0, window);
       long windowStartPositionUs = window.getDefaultPositionUs();
       if (deferredMediaPeriod != null) {
         long periodPreparePositionUs = deferredMediaPeriod.getPreparePositionUs();