diff --git a/payload_consumer/install_plan.cc b/payload_consumer/install_plan.cc
index 4a37836..f4bbeb4 100644
--- a/payload_consumer/install_plan.cc
+++ b/payload_consumer/install_plan.cc
@@ -109,18 +109,19 @@
   for (Partition& partition : partitions) {
     if (source_slot != BootControlInterface::kInvalidSlot &&
         partition.source_size > 0) {
-      result = boot_control->GetPartitionDevice(
-                   partition.name, source_slot, &partition.source_path) &&
-               result;
+      TEST_AND_RETURN_FALSE(boot_control->GetPartitionDevice(
+          partition.name, source_slot, &partition.source_path));
     } else {
       partition.source_path.clear();
     }
 
     if (target_slot != BootControlInterface::kInvalidSlot &&
         partition.target_size > 0) {
-      result = boot_control->GetPartitionDevice(
-                   partition.name, target_slot, &partition.target_path) &&
-               result;
+      auto device = boot_control->GetPartitionDevice(
+          partition.name, target_slot, source_slot);
+      TEST_AND_RETURN_FALSE(device.has_value());
+      partition.target_path = device->rw_device_path;
+      partition.postinstall_mount_device = device->mountable_device_path;
     } else {
       partition.target_path.clear();
     }
diff --git a/payload_consumer/install_plan.h b/payload_consumer/install_plan.h
index ee1a72b..7068f6c 100644
--- a/payload_consumer/install_plan.h
+++ b/payload_consumer/install_plan.h
@@ -98,9 +98,17 @@
     uint64_t source_size{0};
     brillo::Blob source_hash;
 
+    // |target_path| is intended to be a path to block device, which you can
+    // open with |open| syscall and perform regular unix style read/write.
+    // For VABC, this will be empty. As you can't read/write VABC devices with
+    // regular syscall.
     std::string target_path;
+    // |mountable_target_device| is intended to be a path to block device which
+    // can be used for mounting this block device's underlying filesystem.
+    std::string postinstall_mount_device;
     uint64_t target_size{0};
     brillo::Blob target_hash;
+
     uint32_t block_size{0};
 
     // Whether we should run the postinstall script from this partition and the
diff --git a/payload_consumer/postinstall_runner_action.cc b/payload_consumer/postinstall_runner_action.cc
index d51241f..bd49639 100644
--- a/payload_consumer/postinstall_runner_action.cc
+++ b/payload_consumer/postinstall_runner_action.cc
@@ -50,7 +50,6 @@
 
 namespace chromeos_update_engine {
 
-using brillo::MessageLoop;
 using std::string;
 using std::vector;
 
@@ -127,7 +126,7 @@
   const InstallPlan::Partition& partition =
       install_plan_.partitions[current_partition_];
 
-  const string mountable_device = partition.target_path;
+  const string mountable_device = partition.postinstall_mount_device;
   if (mountable_device.empty()) {
     LOG(ERROR) << "Cannot make mountable device from " << partition.target_path;
     return CompletePostinstall(ErrorCode::kPostinstallRunnerError);
diff --git a/payload_consumer/postinstall_runner_action_unittest.cc b/payload_consumer/postinstall_runner_action_unittest.cc
index cce86e9..9b330d9 100644
--- a/payload_consumer/postinstall_runner_action_unittest.cc
+++ b/payload_consumer/postinstall_runner_action_unittest.cc
@@ -195,6 +195,7 @@
   InstallPlan::Partition part;
   part.name = "part";
   part.target_path = device_path;
+  part.postinstall_mount_device = device_path;
   part.run_postinstall = true;
   part.postinstall_path = postinstall_program;
   InstallPlan install_plan;
@@ -356,6 +357,7 @@
   InstallPlan::Partition part;
   part.name = "part";
   part.target_path = "/dev/null";
+  part.postinstall_mount_device = "/dev/null";
   part.run_postinstall = true;
   part.postinstall_path = kPostinstallDefaultScript;
   part.postinstall_optional = true;