diff --git a/services/core/java/com/android/server/am/ActivityStack.java b/services/core/java/com/android/server/am/ActivityStack.java
index c9d62224c3c2d..d689a29913a77 100755
--- a/services/core/java/com/android/server/am/ActivityStack.java
+++ b/services/core/java/com/android/server/am/ActivityStack.java
@@ -3624,8 +3624,10 @@ final class ActivityStack {
             if (isOnHomeDisplay()) {
                 mStackSupervisor.moveHomeStack(!isHomeStack());
             }
-            mStacks.remove(this);
-            mStacks.add(0, this);
+            if (mStacks != null) {
+                mStacks.remove(this);
+                mStacks.add(0, this);
+            }
         }
     }