diff --git a/aosp/hardware_android.cc b/aosp/hardware_android.cc
index 0ac82d6..624cfc9 100644
--- a/aosp/hardware_android.cc
+++ b/aosp/hardware_android.cc
@@ -346,4 +346,30 @@
   return error_code;
 }
 
+// Mount options for non-system partitions. This option causes selinux treat
+// every file in the mounted filesystem as having the 'postinstall_file'
+// context, regardless of what the filesystem itself records. See "SELinux
+// User's and Administrator's Guide" for more information on this option.
+constexpr const char* kDefaultPostinstallMountOptions =
+    "context=u:object_r:postinstall_file:s0";
+
+// Mount options for system partitions. This option causes selinux to use the
+// 'postinstall_file' context as a fallback if there are no other selinux
+// contexts associated with the file in the mounted partition. See "SELinux
+// User's and Administrator's Guide" for more information on this option.
+constexpr const char* kSystemPostinstallMountOptions =
+    "defcontext=u:object_r:postinstall_file:s0";
+
+// Name of the system-partition
+constexpr std::string_view kSystemPartitionName = "system";
+
+const char* HardwareAndroid::GetPartitionMountOptions(
+    const std::string& partition_name) const {
+  if (partition_name == kSystemPartitionName) {
+    return kSystemPostinstallMountOptions;
+  } else {
+    return kDefaultPostinstallMountOptions;
+  }
+}
+
 }  // namespace chromeos_update_engine
diff --git a/aosp/hardware_android.h b/aosp/hardware_android.h
index 78f056e..d20e8df 100644
--- a/aosp/hardware_android.h
+++ b/aosp/hardware_android.h
@@ -64,6 +64,8 @@
   [[nodiscard]] ErrorCode IsPartitionUpdateValid(
       const std::string& partition_name,
       const std::string& new_version) const override;
+  [[nodiscard]] const char* GetPartitionMountOptions(
+      const std::string& partition_name) const override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(HardwareAndroid);
diff --git a/aosp/platform_constants_android.cc b/aosp/platform_constants_android.cc
index f468c3b..a0a2a5e 100644
--- a/aosp/platform_constants_android.cc
+++ b/aosp/platform_constants_android.cc
@@ -31,8 +31,6 @@
 // No deadline file API support on Android.
 const char kOmahaResponseDeadlineFile[] = "";
 const char kNonVolatileDirectory[] = "/data/misc/update_engine";
-const char kPostinstallMountOptions[] =
-    "context=u:object_r:postinstall_file:s0";
 
 }  // namespace constants
 }  // namespace chromeos_update_engine