diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index f68d00c1da..446dffd535 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -7,6 +7,12 @@
         information ([#8560](https://github.com/google/ExoPlayer/issues/8560)).
 *   UI:
     *   Add builder for `PlayerNotificationManager`.
+*   IMA extension:
+    *   Fix handling of repeated ad loads, to avoid ads being discarded if the
+        user seeks away and then back to a preloaded postroll (for example).
+    *   Fix a bug where an assertion would fail if the player started to buffer
+        an ad media period before the ad URI was known then an ad state update
+        arrived that didn't set the ad URI.
 
 ### 2.13.0 (2021-02-04)
 
diff --git a/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/AdTagLoader.java b/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/AdTagLoader.java
index 4ce0610fb6..624a009bb7 100644
--- a/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/AdTagLoader.java
+++ b/extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/AdTagLoader.java
@@ -879,7 +879,8 @@ import java.util.Map;
     int adGroupIndex = getAdGroupIndexForAdPod(adPodInfo);
     int adIndexInAdGroup = adPodInfo.getAdPosition() - 1;
     AdInfo adInfo = new AdInfo(adGroupIndex, adIndexInAdGroup);
-    adInfoByAdMediaInfo.put(adMediaInfo, adInfo);
+    // The ad URI may already be known, so force put to update it if needed.
+    adInfoByAdMediaInfo.forcePut(adMediaInfo, adInfo);
     if (configuration.debugModeEnabled) {
       Log.d(TAG, "loadAd " + getAdMediaInfoString(adMediaInfo));
     }
diff --git a/library/common/src/main/java/com/google/android/exoplayer2/source/ads/AdPlaybackState.java b/library/common/src/main/java/com/google/android/exoplayer2/source/ads/AdPlaybackState.java
index a50fcd7d1d..b70dd10c38 100644
--- a/library/common/src/main/java/com/google/android/exoplayer2/source/ads/AdPlaybackState.java
+++ b/library/common/src/main/java/com/google/android/exoplayer2/source/ads/AdPlaybackState.java
@@ -182,9 +182,10 @@ public final class AdPlaybackState {
     /** Returns a new instance with the specified ad durations, in microseconds. */
     @CheckResult
     public AdGroup withAdDurationsUs(long[] durationsUs) {
-      Assertions.checkArgument(count == C.LENGTH_UNSET || durationsUs.length <= this.uris.length);
-      if (durationsUs.length < this.uris.length) {
+      if (durationsUs.length < uris.length) {
         durationsUs = copyDurationsUsWithSpaceForAdCount(durationsUs, uris.length);
+      } else if (count != C.LENGTH_UNSET && durationsUs.length > uris.length) {
+        durationsUs = Arrays.copyOf(durationsUs, uris.length);
       }
       return new AdGroup(count, states, uris, durationsUs);
     }