diff --git a/aosp/cleanup_previous_update_action.cc b/aosp/cleanup_previous_update_action.cc
index 2aba9bf..fb7bac1 100644
--- a/aosp/cleanup_previous_update_action.cc
+++ b/aosp/cleanup_previous_update_action.cc
@@ -328,6 +328,7 @@
 
     case UpdateState::MergeCompleted: {
       LOG(INFO) << "Merge finished with state MergeCompleted.";
+      boot_control_->MarkSlotUnbootable(1 - boot_control_->GetCurrentSlot());
       processor_->ActionComplete(this, ErrorCode::kSuccess);
       return;
     }