diff --git a/src/com/android/settings/accessibility/FloatingMenuSizePreferenceController.java b/src/com/android/settings/accessibility/FloatingMenuSizePreferenceController.java
index bd447be1d1d..7d4f495f5a8 100644
--- a/src/com/android/settings/accessibility/FloatingMenuSizePreferenceController.java
+++ b/src/com/android/settings/accessibility/FloatingMenuSizePreferenceController.java
@@ -52,11 +52,12 @@ public class FloatingMenuSizePreferenceController extends BasePreferenceControll
 
     @Retention(RetentionPolicy.SOURCE)
     @IntDef({
+            Size.UNKNOWN,
             Size.SMALL,
             Size.LARGE,
     })
-    @VisibleForTesting
-    @interface Size {
+    public @interface Size {
+        int UNKNOWN = -1;
         int SMALL = 0;
         int LARGE = 1;
     }
diff --git a/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java b/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java
index e05943c5bce..a485b494ddb 100644
--- a/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java
+++ b/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragment.java
@@ -643,6 +643,17 @@ public class ToggleScreenMagnificationPreferenceFragment extends
         joiner.add(MAGNIFICATION_CONTROLLER_NAME);
 
         Settings.Secure.putString(context.getContentResolver(), targetKey, joiner.toString());
+        // The size setting defaults to unknown. If the user has ever manually changed the size
+        // before, we do not automatically change it.
+        if (shortcutType == UserShortcutType.SOFTWARE
+                && Settings.Secure.getInt(context.getContentResolver(),
+                Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE,
+                FloatingMenuSizePreferenceController.Size.UNKNOWN)
+                == FloatingMenuSizePreferenceController.Size.UNKNOWN) {
+            Settings.Secure.putInt(context.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE,
+                    FloatingMenuSizePreferenceController.Size.LARGE);
+        }
     }
 
     @VisibleForTesting
diff --git a/tests/robotests/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragmentTest.java b/tests/robotests/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragmentTest.java
index a4033b1127b..2eac7851688 100644
--- a/tests/robotests/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragmentTest.java
+++ b/tests/robotests/src/com/android/settings/accessibility/ToggleScreenMagnificationPreferenceFragmentTest.java
@@ -64,6 +64,7 @@ import org.robolectric.Shadows;
 import org.robolectric.annotation.Config;
 import org.robolectric.shadows.ShadowContentResolver;
 import org.robolectric.shadows.ShadowPackageManager;
+import org.robolectric.shadows.ShadowSettings;
 import org.robolectric.shadows.androidx.fragment.FragmentController;
 import org.robolectric.util.ReflectionHelpers;
 
@@ -71,7 +72,8 @@ import java.util.Collection;
 import java.util.List;
 
 /** Tests for {@link ToggleScreenMagnificationPreferenceFragment}. */
-@Config(shadows = {ShadowUserManager.class, ShadowStorageManager.class})
+@Config(shadows = {ShadowUserManager.class, ShadowStorageManager.class,
+        ShadowSettings.ShadowSecure.class})
 @RunWith(RobolectricTestRunner.class)
 public class ToggleScreenMagnificationPreferenceFragmentTest {
 
@@ -208,6 +210,73 @@ public class ToggleScreenMagnificationPreferenceFragmentTest {
                 PLACEHOLDER_COMPONENT_NAME.flattenToString() + ":" + MAGNIFICATION_CONTROLLER_NAME);
     }
 
+    @Test
+    public void optInAllValuesToSettings_software_sizeValueIsNull_putLargeSizeValue() {
+        ShadowSettings.ShadowSecure.reset();
+
+        ToggleScreenMagnificationPreferenceFragment.optInAllMagnificationValuesToSettings(mContext,
+                UserShortcutType.SOFTWARE);
+
+        assertThat(Settings.Secure.getInt(mContext.getContentResolver(),
+                Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE,
+                FloatingMenuSizePreferenceController.Size.UNKNOWN)).isEqualTo(
+                FloatingMenuSizePreferenceController.Size.LARGE);
+    }
+
+    @Test
+    public void optInAllValuesToSettings_software_sizeValueIsNotNull_sizeValueIsNotChanged() {
+        for (int size : new int[] {FloatingMenuSizePreferenceController.Size.LARGE,
+                FloatingMenuSizePreferenceController.Size.SMALL}) {
+            Settings.Secure.putInt(mContext.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE, size);
+
+            ToggleScreenMagnificationPreferenceFragment.optInAllMagnificationValuesToSettings(
+                    mContext,
+                    UserShortcutType.SOFTWARE);
+
+            assertThat(Settings.Secure.getInt(mContext.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE,
+                    FloatingMenuSizePreferenceController.Size.UNKNOWN)).isEqualTo(
+                    size);
+        }
+    }
+
+    @Test
+    public void optInAllValuesToSettings_hardware_sizeValueIsNotChanged() {
+        for (int size : new int[] {FloatingMenuSizePreferenceController.Size.UNKNOWN,
+                FloatingMenuSizePreferenceController.Size.LARGE,
+                FloatingMenuSizePreferenceController.Size.SMALL}) {
+            Settings.Secure.putInt(mContext.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE, size);
+
+            ToggleScreenMagnificationPreferenceFragment.optInAllMagnificationValuesToSettings(
+                    mContext,
+                    UserShortcutType.HARDWARE);
+
+            assertThat(Settings.Secure.getInt(mContext.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE, size + 1)).isEqualTo(
+                    size);
+        }
+    }
+
+    @Test
+    public void optInAllValuesToSettings_tripletap_sizeValueIsNotChanged() {
+        for (int size : new int[] {FloatingMenuSizePreferenceController.Size.UNKNOWN,
+                FloatingMenuSizePreferenceController.Size.LARGE,
+                FloatingMenuSizePreferenceController.Size.SMALL}) {
+            Settings.Secure.putInt(mContext.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE, size);
+
+            ToggleScreenMagnificationPreferenceFragment.optInAllMagnificationValuesToSettings(
+                    mContext,
+                    UserShortcutType.TRIPLETAP);
+
+            assertThat(Settings.Secure.getInt(mContext.getContentResolver(),
+                    Settings.Secure.ACCESSIBILITY_FLOATING_MENU_SIZE, size + 1)).isEqualTo(
+                    size);
+        }
+    }
+
     @Test
     public void optOutAllValuesToSettings_optOutValue_emptyString() {
         putStringIntoSettings(SOFTWARE_SHORTCUT_KEY, MAGNIFICATION_CONTROLLER_NAME);