diff --git a/services/core/java/com/android/server/wm/RootDisplayArea.java b/services/core/java/com/android/server/wm/RootDisplayArea.java
index cd20c8242d81b..1cda8d56ddc72 100644
--- a/services/core/java/com/android/server/wm/RootDisplayArea.java
+++ b/services/core/java/com/android/server/wm/RootDisplayArea.java
@@ -37,7 +37,7 @@ import java.util.Map;
  * of the whole logical display, or a {@link DisplayAreaGroup} as the root of a partition of the
  * logical display.
  */
-class RootDisplayArea extends DisplayArea<DisplayArea> {
+class RootDisplayArea extends DisplayArea.Dimmable {
 
     /** {@link Feature} that are supported in this {@link DisplayArea} hierarchy. */
     List<DisplayAreaPolicyBuilder.Feature> mFeatures;
diff --git a/services/tests/wmtests/src/com/android/server/wm/TaskTests.java b/services/tests/wmtests/src/com/android/server/wm/TaskTests.java
index 2389d2d6e8d64..13ef9982494eb 100644
--- a/services/tests/wmtests/src/com/android/server/wm/TaskTests.java
+++ b/services/tests/wmtests/src/com/android/server/wm/TaskTests.java
@@ -80,6 +80,7 @@ import android.util.DisplayMetrics;
 import android.util.TypedXmlPullParser;
 import android.util.TypedXmlSerializer;
 import android.util.Xml;
+import android.view.Display;
 import android.view.DisplayInfo;
 
 import androidx.test.filters.MediumTest;
@@ -1338,6 +1339,16 @@ public class TaskTests extends WindowTestsBase {
         verify(display).onDescendantOrientationChanged(same(task));
     }
 
+    @Test
+    public void testGetNonNullDimmerOnUntrustedDisplays() {
+        final DisplayInfo untrustedDisplayInfo = new DisplayInfo(mDisplayInfo);
+        untrustedDisplayInfo.flags &= ~Display.FLAG_TRUSTED;
+        final DisplayContent untrustedDisplay = createNewDisplay(untrustedDisplayInfo);
+        final ActivityRecord activity = createActivityRecord(untrustedDisplay);
+        activity.setOccludesParent(false);
+        assertNotNull(activity.getTask().getDimmer());
+    }
+
     private Task getTestTask() {
         final Task task = new TaskBuilder(mSupervisor).setCreateActivity(true).build();
         return task.getBottomMostTask();