diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 970d275ac15a3..9f1ce0b44501f 100755
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -8852,7 +8852,8 @@ public final class ActivityManagerService extends ActivityManagerNative
                 task = mStackSupervisor.anyTaskForIdLocked(task.taskId);
                 if (task != null) {
                     if (!isSystemInitiated
-                            && ((mFocusedActivity == null) || (task != mFocusedActivity.task))) {
+                            && ((mStackSupervisor.getFocusedStack() == null)
+                                    || (task != mStackSupervisor.getFocusedStack().topTask()))) {
                         throw new IllegalArgumentException("Invalid task, not in foreground");
                     }
                     mStackSupervisor.setLockTaskModeLocked(task, !isSystemInitiated);