diff --git a/aosp/update_attempter_android.cc b/aosp/update_attempter_android.cc
index ba61f25..2ffa0da 100644
--- a/aosp/update_attempter_android.cc
+++ b/aosp/update_attempter_android.cc
@@ -884,20 +884,25 @@
   string current_version =
       android::base::GetProperty("ro.build.version.incremental", "");
   TEST_AND_RETURN(!current_version.empty());
+  const auto current_slot = boot_control_->GetCurrentSlot();
 
   // If there's no record of previous version (e.g. due to a data wipe), we
   // save the info of current boot and skip the metrics report.
   if (!prefs_->Exists(kPrefsPreviousVersion)) {
     prefs_->SetString(kPrefsBootId, current_boot_id);
     prefs_->SetString(kPrefsPreviousVersion, current_version);
+    prefs_->SetInt64(std::string{kPrefsPreviousSlot},
+                     boot_control_->GetCurrentSlot());
     ClearMetricsPrefs();
     return;
   }
+  int64_t previous_slot = -1;
+  prefs_->GetInt64(kPrefsPreviousSlot, &previous_slot);
   string previous_version;
-  // update_engine restarted under the same build.
+  // update_engine restarted under the same build and same slot.
   // TODO(xunchang) identify and report rollback by checking UpdateMarker.
   if (prefs_->GetString(kPrefsPreviousVersion, &previous_version) &&
-      previous_version == current_version) {
+      previous_version == current_version && previous_slot == current_slot) {
     string last_boot_id;
     bool is_reboot = prefs_->Exists(kPrefsBootId) &&
                      (prefs_->GetString(kPrefsBootId, &last_boot_id) &&
@@ -917,6 +922,8 @@
   // TODO(xunchang) check the build version is larger than the previous one.
   prefs_->SetString(kPrefsBootId, current_boot_id);
   prefs_->SetString(kPrefsPreviousVersion, current_version);
+  prefs_->SetInt64(std::string{kPrefsPreviousSlot},
+                   boot_control_->GetCurrentSlot());
 
   bool previous_attempt_exists = prefs_->Exists(kPrefsPayloadAttemptNumber);
   // |kPrefsPayloadAttemptNumber| should be cleared upon successful update.
diff --git a/aosp/update_attempter_android_unittest.cc b/aosp/update_attempter_android_unittest.cc
index f799df3..f73df16 100644
--- a/aosp/update_attempter_android_unittest.cc
+++ b/aosp/update_attempter_android_unittest.cc
@@ -24,6 +24,7 @@
 #include <base/time/time.h>
 #include <gtest/gtest.h>
 
+#include "common/constants.h"
 #include "update_engine/aosp/daemon_state_android.h"
 #include "update_engine/common/fake_boot_control.h"
 #include "update_engine/common/fake_clock.h"
@@ -81,6 +82,8 @@
   prefs_.SetString(kPrefsPreviousVersion, build_version);
   prefs_.SetString(kPrefsBootId, "oldboot");
   prefs_.SetInt64(kPrefsNumReboots, 1);
+  prefs_.SetInt64(kPrefsPreviousSlot, 1);
+  boot_control_.SetCurrentSlot(1);
 
   EXPECT_CALL(*metrics_reporter_, ReportTimeToReboot(_)).Times(0);
   update_attempter_android_.Init();
@@ -88,15 +91,15 @@
   // Check that the boot_id and reboot_count are updated.
   std::string boot_id;
   utils::GetBootId(&boot_id);
-  EXPECT_TRUE(prefs_.Exists(kPrefsBootId));
+  ASSERT_TRUE(prefs_.Exists(kPrefsBootId));
   std::string prefs_boot_id;
-  EXPECT_TRUE(prefs_.GetString(kPrefsBootId, &prefs_boot_id));
-  EXPECT_EQ(boot_id, prefs_boot_id);
+  ASSERT_TRUE(prefs_.GetString(kPrefsBootId, &prefs_boot_id));
+  ASSERT_EQ(boot_id, prefs_boot_id);
 
-  EXPECT_TRUE(prefs_.Exists(kPrefsNumReboots));
+  ASSERT_TRUE(prefs_.Exists(kPrefsNumReboots));
   int64_t reboot_count;
-  EXPECT_TRUE(prefs_.GetInt64(kPrefsNumReboots, &reboot_count));
-  EXPECT_EQ(2, reboot_count);
+  ASSERT_TRUE(prefs_.GetInt64(kPrefsNumReboots, &reboot_count));
+  ASSERT_EQ(2, reboot_count);
 }
 
 TEST_F(UpdateAttempterAndroidTest, UpdatePrefsBuildVersionChangeOnInit) {