diff --git a/services/accessibility/java/com/android/server/accessibility/magnification/FullScreenMagnificationController.java b/services/accessibility/java/com/android/server/accessibility/magnification/FullScreenMagnificationController.java
index 6b6b39d..a77ba62 100644
--- a/services/accessibility/java/com/android/server/accessibility/magnification/FullScreenMagnificationController.java
+++ b/services/accessibility/java/com/android/server/accessibility/magnification/FullScreenMagnificationController.java
@@ -47,7 +47,6 @@
 import android.util.Slog;
 import android.util.SparseArray;
 import android.util.TypedValue;
-import android.view.Display;
 import android.view.DisplayInfo;
 import android.view.MagnificationSpec;
 import android.view.View;
@@ -1637,9 +1636,10 @@
      * <strong>if scale is >= {@link MagnificationConstants.PERSISTED_SCALE_MIN_VALUE}</strong>.
      * We assume if the scale is < {@link MagnificationConstants.PERSISTED_SCALE_MIN_VALUE}, there
      * will be no obvious magnification effect.
+     * Only the value of the default display is persisted in user's settings.
      */
     public void persistScale(int displayId) {
-        final float scale = getScale(Display.DEFAULT_DISPLAY);
+        final float scale = getScale(displayId);
         if (scale < MagnificationConstants.PERSISTED_SCALE_MIN_VALUE) {
             return;
         }
diff --git a/services/tests/servicestests/src/com/android/server/accessibility/magnification/FullScreenMagnificationControllerTest.java b/services/tests/servicestests/src/com/android/server/accessibility/magnification/FullScreenMagnificationControllerTest.java
index 1426d5d..c4b4afd 100644
--- a/services/tests/servicestests/src/com/android/server/accessibility/magnification/FullScreenMagnificationControllerTest.java
+++ b/services/tests/servicestests/src/com/android/server/accessibility/magnification/FullScreenMagnificationControllerTest.java
@@ -69,6 +69,7 @@
 import androidx.test.runner.AndroidJUnit4;
 
 import com.android.internal.R;
+import com.android.internal.os.BackgroundThread;
 import com.android.internal.util.ConcurrentUtils;
 import com.android.internal.util.test.FakeSettingsProvider;
 import com.android.server.LocalServices;
@@ -92,6 +93,8 @@
 import org.testng.Assert;
 
 import java.util.Locale;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
 
 @RunWith(AndroidJUnit4.class)
 public class FullScreenMagnificationControllerTest {
@@ -1440,19 +1443,42 @@
 
     @Test
     public void persistScale_setValueWhenScaleIsOne_nothingChanged() {
+        register(TEST_DISPLAY);
         final float persistedScale =
                 mFullScreenMagnificationController.getPersistedScale(TEST_DISPLAY);
 
         PointF pivotPoint = INITIAL_BOUNDS_LOWER_RIGHT_2X_CENTER;
-        mFullScreenMagnificationController.setScale(DISPLAY_0, 1.0f, pivotPoint.x, pivotPoint.y,
+        mFullScreenMagnificationController.setScale(TEST_DISPLAY, 1.0f, pivotPoint.x, pivotPoint.y,
                 false, SERVICE_ID_1);
         mFullScreenMagnificationController.persistScale(TEST_DISPLAY);
 
+        // persistScale may post a task to a background thread. Let's wait for it completes.
+        waitForBackgroundThread();
         Assert.assertEquals(mFullScreenMagnificationController.getPersistedScale(TEST_DISPLAY),
                 persistedScale);
     }
 
     @Test
+    public void persistScale_setValuesOnMultipleDisplays() {
+        register(DISPLAY_0);
+        register(DISPLAY_1);
+        final PointF pivotPoint = INITIAL_BOUNDS_LOWER_RIGHT_2X_CENTER;
+        mFullScreenMagnificationController.setScale(DISPLAY_0, 3.0f, pivotPoint.x, pivotPoint.y,
+                false, SERVICE_ID_1);
+        mFullScreenMagnificationController.persistScale(DISPLAY_0);
+        mFullScreenMagnificationController.setScale(DISPLAY_1, 4.0f, pivotPoint.x, pivotPoint.y,
+                false, SERVICE_ID_1);
+        mFullScreenMagnificationController.persistScale(DISPLAY_1);
+
+        // persistScale may post a task to a background thread. Let's wait for it completes.
+        waitForBackgroundThread();
+        Assert.assertEquals(mFullScreenMagnificationController.getPersistedScale(DISPLAY_0),
+                3.0f);
+        Assert.assertEquals(mFullScreenMagnificationController.getPersistedScale(DISPLAY_1),
+                4.0f);
+    }
+
+    @Test
     public void testOnContextChanged_alwaysOnFeatureDisabled_resetMagnification() {
         setScaleToMagnifying();
 
@@ -1494,6 +1520,15 @@
         );
     }
 
+    private static void waitForBackgroundThread() {
+        final CompletableFuture<Void> future = new CompletableFuture<>();
+        BackgroundThread.getHandler().post(() -> future.complete(null));
+        try {
+            future.get();
+        } catch (InterruptedException | ExecutionException ignore) {
+        }
+    }
+
     private void setScaleToMagnifying() {
         register(DISPLAY_0);
         float scale = 2.0f;