diff --git a/quickstep/src/com/android/quickstep/TaskThumbnailCache.kt b/quickstep/src/com/android/quickstep/TaskThumbnailCache.kt
index 7b56213454..1d880ab6a9 100644
--- a/quickstep/src/com/android/quickstep/TaskThumbnailCache.kt
+++ b/quickstep/src/com/android/quickstep/TaskThumbnailCache.kt
@@ -119,7 +119,7 @@ internal constructor(
                 highResLoadingState.isEnabled
         ) {
             val newCachedThumbnail = cache.getAndInvalidateIfModified(task.key)
-            if (newCachedThumbnail.thumbnail != null && !newCachedThumbnail.reducedResolution) {
+            if (newCachedThumbnail?.thumbnail != null && !newCachedThumbnail.reducedResolution) {
                 return newCachedThumbnail
             }
         }
diff --git a/quickstep/src/com/android/quickstep/util/TaskKeyByLastActiveTimeCache.java b/quickstep/src/com/android/quickstep/util/TaskKeyByLastActiveTimeCache.java
index 69137cc1b6..43ef39c256 100644
--- a/quickstep/src/com/android/quickstep/util/TaskKeyByLastActiveTimeCache.java
+++ b/quickstep/src/com/android/quickstep/util/TaskKeyByLastActiveTimeCache.java
@@ -17,6 +17,7 @@ package com.android.quickstep.util;
 
 import android.util.Log;
 
+import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 
 import com.android.systemui.shared.recents.model.Task;
@@ -94,6 +95,7 @@ public class TaskKeyByLastActiveTimeCache<V> implements TaskKeyCache<V> {
      * Gets the entry if it is still valid
      */
     @Override
+    @Nullable
     public synchronized V getAndInvalidateIfModified(Task.TaskKey key) {
         Entry<V> entry = mMap.get(key.id);
         if (entry != null && entry.mKey.windowingMode == key.windowingMode
diff --git a/quickstep/src/com/android/quickstep/util/TaskKeyCache.java b/quickstep/src/com/android/quickstep/util/TaskKeyCache.java
index 8ee78ab0ba..9df0993a7b 100644
--- a/quickstep/src/com/android/quickstep/util/TaskKeyCache.java
+++ b/quickstep/src/com/android/quickstep/util/TaskKeyCache.java
@@ -15,6 +15,8 @@
  */
 package com.android.quickstep.util;
 
+import androidx.annotation.Nullable;
+
 import com.android.systemui.shared.recents.model.Task;
 
 import java.util.function.Predicate;
@@ -44,6 +46,7 @@ public interface TaskKeyCache<V> {
     /**
      * Gets the entry if it is still valid.
      */
+    @Nullable
     V getAndInvalidateIfModified(Task.TaskKey key);
 
     /**
diff --git a/quickstep/src/com/android/quickstep/util/TaskKeyLruCache.java b/quickstep/src/com/android/quickstep/util/TaskKeyLruCache.java
index 89f5d41dad..9fe8cc954d 100644
--- a/quickstep/src/com/android/quickstep/util/TaskKeyLruCache.java
+++ b/quickstep/src/com/android/quickstep/util/TaskKeyLruCache.java
@@ -17,6 +17,8 @@ package com.android.quickstep.util;
 
 import android.util.Log;
 
+import androidx.annotation.Nullable;
+
 import com.android.systemui.shared.recents.model.Task.TaskKey;
 
 import java.util.LinkedHashMap;
@@ -59,6 +61,7 @@ public class TaskKeyLruCache<V> implements TaskKeyCache<V> {
     /**
      * Gets the entry if it is still valid
      */
+    @Nullable
     public synchronized V getAndInvalidateIfModified(TaskKey key) {
         Entry<V> entry = mMap.get(key.id);