diff --git a/packages/SystemUI/src/com/android/systemui/ForegroundServiceController.java b/packages/SystemUI/src/com/android/systemui/ForegroundServiceController.java
index 15a5c2773f0b9..c1a23c8ab0035 100644
--- a/packages/SystemUI/src/com/android/systemui/ForegroundServiceController.java
+++ b/packages/SystemUI/src/com/android/systemui/ForegroundServiceController.java
@@ -27,6 +27,7 @@ import com.android.systemui.appops.AppOpsController;
 import com.android.systemui.dagger.qualifiers.MainHandler;
 import com.android.systemui.statusbar.notification.NotificationEntryManager;
 import com.android.systemui.statusbar.notification.collection.NotificationEntry;
+import com.android.systemui.util.Assert;
 
 import javax.inject.Inject;
 import javax.inject.Singleton;
@@ -121,6 +122,8 @@ public class ForegroundServiceController {
      * @param active whether the appOpCode is active or not
      */
     void onAppOpChanged(int appOpCode, int uid, String packageName, boolean active) {
+        Assert.isMainThread();
+
         int userId = UserHandle.getUserId(uid);
         // Record active app ops
         synchronized (mMutex) {
diff --git a/packages/SystemUI/tests/src/com/android/systemui/ForegroundServiceControllerTest.java b/packages/SystemUI/tests/src/com/android/systemui/ForegroundServiceControllerTest.java
index 02a3766fb3b6c..0990e2274d8a0 100644
--- a/packages/SystemUI/tests/src/com/android/systemui/ForegroundServiceControllerTest.java
+++ b/packages/SystemUI/tests/src/com/android/systemui/ForegroundServiceControllerTest.java
@@ -18,6 +18,7 @@ package com.android.systemui;
 
 import static junit.framework.Assert.assertEquals;
 import static junit.framework.Assert.assertNull;
+import static junit.framework.TestCase.fail;
 
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -34,12 +35,14 @@ import android.app.Notification;
 import android.app.NotificationManager;
 import android.os.Bundle;
 import android.os.Handler;
+import android.os.Looper;
 import android.os.UserHandle;
 import android.service.notification.StatusBarNotification;
+import android.testing.AndroidTestingRunner;
+import android.testing.TestableLooper;
 import android.widget.RemoteViews;
 
 import androidx.test.filters.SmallTest;
-import androidx.test.runner.AndroidJUnit4;
 
 import com.android.internal.messages.nano.SystemMessageProto;
 import com.android.systemui.appops.AppOpsController;
@@ -58,7 +61,8 @@ import org.mockito.Mock;
 import org.mockito.MockitoAnnotations;
 
 @SmallTest
-@RunWith(AndroidJUnit4.class)
+@RunWith(AndroidTestingRunner.class)
+@TestableLooper.RunWithLooper
 public class ForegroundServiceControllerTest extends SysuiTestCase {
     private ForegroundServiceController mFsc;
     private ForegroundServiceNotificationListener mListener;
@@ -69,6 +73,9 @@ public class ForegroundServiceControllerTest extends SysuiTestCase {
 
     @Before
     public void setUp() throws Exception {
+        // assume the TestLooper is the main looper for these tests
+        com.android.systemui.util.Assert.sMainLooper = TestableLooper.get(this).getLooper();
+
         MockitoAnnotations.initMocks(this);
         mFsc = new ForegroundServiceController(mEntryManager, mAppOpsController, mMainHandler);
         mListener = new ForegroundServiceNotificationListener(
@@ -80,6 +87,26 @@ public class ForegroundServiceControllerTest extends SysuiTestCase {
         mEntryListener = entryListenerCaptor.getValue();
     }
 
+    @Test
+    public void testAppOpsChangedCalledFromBgThread() {
+        try {
+            // WHEN onAppOpChanged is called from a different thread than the MainLooper
+            com.android.systemui.util.Assert.sMainLooper = Looper.getMainLooper();
+            NotificationEntry entry = createFgEntry();
+            mFsc.onAppOpChanged(
+                    AppOpsManager.OP_CAMERA,
+                    entry.getSbn().getUid(),
+                    entry.getSbn().getPackageName(),
+                    true);
+
+            // This test is run on the TestableLooper, which is not the MainLooper, so
+            // we expect an exception to be thrown
+            fail("onAppOpChanged shouldn't be allowed to be called from a bg thread.");
+        } catch (IllegalStateException e) {
+            // THEN expect an exception
+        }
+    }
+
     @Test
     public void testAppOps_appOpChangedBeforeNotificationExists() {
         // GIVEN app op exists, but notification doesn't exist in NEM yet