diff --git a/services/accessibility/accessibility.aconfig b/services/accessibility/accessibility.aconfig
index 1c57dd3..9353150 100644
--- a/services/accessibility/accessibility.aconfig
+++ b/services/accessibility/accessibility.aconfig
@@ -220,3 +220,13 @@
     description: "Feature allows users to change color correction saturation for daltonizer."
     bug: "322829049"
 }
+
+flag {
+    name: "skip_package_change_before_user_switch"
+    namespace: "accessibility"
+    description: "Skip onSomePackageChanged callback if the SwitchUser signal is not received yet."
+    bug: "340927041"
+    metadata {
+        purpose: PURPOSE_BUGFIX
+    }
+}
diff --git a/services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java b/services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java
index 053a1a7..20b727c 100644
--- a/services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java
+++ b/services/accessibility/java/com/android/server/accessibility/AccessibilityManagerService.java
@@ -588,6 +588,15 @@
         return Thread.holdsLock(mLock);
     }
 
+    /**
+     * Returns if the service is initialized.
+     *
+     * The service is considered initialized when the user switch happened.
+     */
+    private boolean isServiceInitializedLocked() {
+        return mInitialized;
+    }
+
     @Override
     public int getCurrentUserIdLocked() {
         return mCurrentUserId;
@@ -6234,6 +6243,15 @@
                 if (userId != mManagerService.getCurrentUserIdLocked()) {
                     return;
                 }
+
+                // Only continue setting up the packages if the service has been initialized.
+                // See: b/340927041
+                if (Flags.skipPackageChangeBeforeUserSwitch()
+                        && !mManagerService.isServiceInitializedLocked()) {
+                    Slog.w(LOG_TAG,
+                            "onSomePackagesChanged: service not initialized, skip the callback.");
+                    return;
+                }
                 mManagerService.onSomePackagesChangedLocked(parsedAccessibilityServiceInfos,
                         parsedAccessibilityShortcutInfos);
             }
diff --git a/services/tests/servicestests/src/com/android/server/accessibility/AccessibilityManagerServiceTest.java b/services/tests/servicestests/src/com/android/server/accessibility/AccessibilityManagerServiceTest.java
index f971f0e..4e8c755 100644
--- a/services/tests/servicestests/src/com/android/server/accessibility/AccessibilityManagerServiceTest.java
+++ b/services/tests/servicestests/src/com/android/server/accessibility/AccessibilityManagerServiceTest.java
@@ -923,6 +923,8 @@
         ResolveInfo resolveInfo1 = installedService1.getResolveInfo();
         AccessibilityServiceInfo installedService2 =
                 mA11yms.getCurrentUserState().mInstalledServices.getLast();
+        // Invokes client change to trigger onUserStateChanged.
+        mA11yms.onClientChangeLocked(false);
 
         // Disables `installedService2`
         when(mMockPackageManager.queryIntentServicesAsUser(any(), anyInt(), anyInt()))