diff --git a/payload_consumer/postinstall_runner_action.cc b/payload_consumer/postinstall_runner_action.cc
index d452a64..6a6d687 100644
--- a/payload_consumer/postinstall_runner_action.cc
+++ b/payload_consumer/postinstall_runner_action.cc
@@ -53,6 +53,18 @@
 using std::string;
 using std::vector;
 
+PostinstallRunnerAction::PostinstallRunnerAction(
+    BootControlInterface* boot_control, HardwareInterface* hardware)
+    : boot_control_(boot_control), hardware_(hardware) {
+#ifdef __ANDROID__
+  fs_mount_dir_ = "/postinstall";
+#else   // __ANDROID__
+  base::FilePath temp_dir;
+  TEST_AND_RETURN(base::CreateNewTempDirectory("au_postint_mount", &temp_dir));
+  fs_mount_dir_ = temp_dir.value();
+#endif  // __ANDROID__
+}
+
 void PostinstallRunnerAction::PerformAction() {
   CHECK(HasInputObject());
   CHECK(boot_control_);
@@ -135,13 +147,6 @@
   // Perform post-install for the current_partition_ partition. At this point we
   // need to call CompletePartitionPostinstall to complete the operation and
   // cleanup.
-#ifdef __ANDROID__
-  fs_mount_dir_ = "/postinstall";
-#else   // __ANDROID__
-  base::FilePath temp_dir;
-  TEST_AND_RETURN(base::CreateNewTempDirectory("au_postint_mount", &temp_dir));
-  fs_mount_dir_ = temp_dir.value();
-#endif  // __ANDROID__
 
   if (!utils::FileExists(fs_mount_dir_.c_str())) {
     LOG(ERROR) << "Mount point " << fs_mount_dir_
diff --git a/payload_consumer/postinstall_runner_action.h b/payload_consumer/postinstall_runner_action.h
index e404107..178d72a 100644
--- a/payload_consumer/postinstall_runner_action.h
+++ b/payload_consumer/postinstall_runner_action.h
@@ -19,6 +19,7 @@
 
 #include <memory>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <base/files/file_descriptor_watcher_posix.h>
@@ -40,8 +41,7 @@
 class PostinstallRunnerAction : public InstallPlanAction {
  public:
   PostinstallRunnerAction(BootControlInterface* boot_control,
-                          HardwareInterface* hardware)
-      : boot_control_(boot_control), hardware_(hardware) {}
+                          HardwareInterface* hardware);
 
   // InstallPlanAction overrides.
   void PerformAction() override;
@@ -68,6 +68,9 @@
   friend class PostinstallRunnerActionTest;
   FRIEND_TEST(PostinstallRunnerActionTest, ProcessProgressLineTest);
 
+  // exposed for testing purposes only
+  void SetMountDir(std::string dir) { fs_mount_dir_ = std::move(dir); }
+
   void PerformPartitionPostinstall();
 
   // Called whenever the |progress_fd_| has data available to read.
diff --git a/payload_consumer/postinstall_runner_action_unittest.cc b/payload_consumer/postinstall_runner_action_unittest.cc
index 9b330d9..a9ed5b1 100644
--- a/payload_consumer/postinstall_runner_action_unittest.cc
+++ b/payload_consumer/postinstall_runner_action_unittest.cc
@@ -216,6 +216,9 @@
   auto runner_action = std::make_unique<PostinstallRunnerAction>(
       &fake_boot_control_, &fake_hardware_);
   postinstall_action_ = runner_action.get();
+  base::FilePath temp_dir;
+  TEST_AND_RETURN(base::CreateNewTempDirectory("postinstall", &temp_dir));
+  postinstall_action_->SetMountDir(temp_dir.value());
   runner_action->set_delegate(setup_action_delegate_);
   BondActions(feeder_action.get(), runner_action.get());
   auto collector_action =