diff --git a/payload_consumer/postinstall_runner_action.cc b/payload_consumer/postinstall_runner_action.cc
index bfdd39e..ad1ffc0 100644
--- a/payload_consumer/postinstall_runner_action.cc
+++ b/payload_consumer/postinstall_runner_action.cc
@@ -180,6 +180,57 @@
   EnsureUnmounted();
 
 #ifdef __ANDROID__
+  // Check the currently installed /system partition to see if it's ever
+  // been mounted R/W. If it has, we'll run backuptool scripts for it
+  // since we can safely assume something on the partition has been
+  // changed and we won't be breaking verity (since it's already been
+  // broken). If it hasn't ever been mounted R/W, we can assume that
+  // the rom that the user is upgrading to will have everything they
+  // need and no addon.d scripts will need to be run to retain stuff
+  // after the upgrade.
+  //
+  // Use the following disk layout info to make the determination
+  // https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout
+  // Super block starts from block 0, offset 0x400
+  //   0x2C: len32 Mount time
+  //   0x30: len32 Write time
+  //   0x34: len16 Number of mounts since the last fsck
+  //   0x38: len16 Magic signature 0xEF53
+
+  string source_path;
+
+  if (install_plan_.source_slot != BootControlInterface::kInvalidSlot) {
+    boot_control_->GetPartitionDevice(partition.name, install_plan_.source_slot, &source_path);
+  }
+
+  uint16_t mount_count = 0;
+
+  if (!source_path.empty()) {
+    brillo::Blob chunk;
+
+    utils::ReadFileChunk(source_path, 0x400 + 0x34, sizeof(uint16_t), &chunk);
+    mount_count = *reinterpret_cast<uint16_t*>(chunk.data());
+  }
+
+  LOG(INFO) << source_path << " has been mounted R/W " << mount_count << " times.";
+
+  if (mount_count > 0) {
+    // Mount the target partition R/W
+    LOG(INFO) << "Running backuptool scripts";
+    utils::MountFilesystem(mountable_device, fs_mount_dir_, MS_NOATIME | MS_NODEV | MS_NODIRATIME,
+                           partition.filesystem_type, "seclabel");
+
+    // Run backuptool script
+    int ret = system("/postinstall/system/bin/backuptool_postinstall.sh");
+    if (ret == -1 || WEXITSTATUS(ret) != 0) {
+      LOG(ERROR) << "Backuptool postinstall step failed. ret=" << ret;
+    }
+  } else {
+    LOG(INFO) << "Skipping backuptool scripts";
+  }
+
+  utils::UnmountFilesystem(fs_mount_dir_);
+
   // In Chromium OS, the postinstall step is allowed to write to the block
   // device on the target image, so we don't mark it as read-only and should
   // be read-write since we just wrote to it during the update.