diff --git a/common/error_code.h b/common/error_code.h
index e08ec46..3800bf0 100644
--- a/common/error_code.h
+++ b/common/error_code.h
@@ -73,6 +73,8 @@
   kFilesystemVerifierError = 47,
   kUserCanceled = 48,
   kNonCriticalUpdateInOOBE = 49,
+  // kOmahaUpdateIgnoredOverCellular = 50,
+  kPayloadTimestampError = 51,
 
   // VERY IMPORTANT! When adding new error codes:
   //
diff --git a/common/error_code_utils.cc b/common/error_code_utils.cc
index ad4aeeb..0a015eb 100644
--- a/common/error_code_utils.cc
+++ b/common/error_code_utils.cc
@@ -144,6 +144,8 @@
       return "ErrorCode::kUserCanceled";
     case ErrorCode::kNonCriticalUpdateInOOBE:
       return "ErrorCode::kNonCriticalUpdateInOOBE";
+    case ErrorCode::kPayloadTimestampError:
+      return "ErrorCode::kPayloadTimestampError";
     // Don't add a default case to let the compiler warn about newly added
     // error codes which should be added here.
   }
diff --git a/common/fake_hardware.h b/common/fake_hardware.h
index 5d0fca3..a384597 100644
--- a/common/fake_hardware.h
+++ b/common/fake_hardware.h
@@ -81,6 +81,8 @@
     return false;
   }
 
+  int64_t GetBuildTimestamp() const override { return build_timestamp_; }
+
   // Setters
   void SetIsOfficialBuild(bool is_official_build) {
     is_official_build_ = is_official_build;
@@ -125,6 +127,10 @@
     powerwash_count_ = powerwash_count;
   }
 
+  void SetBuildTimestamp(int64_t build_timestamp) {
+    build_timestamp_ = build_timestamp;
+  }
+
  private:
   bool is_official_build_{true};
   bool is_normal_boot_mode_{true};
@@ -137,6 +143,7 @@
   std::string ec_version_{"Fake EC v1.0a"};
   int powerwash_count_{kPowerwashCountNotSet};
   bool powerwash_scheduled_{false};
+  int64_t build_timestamp_{0};
 
   DISALLOW_COPY_AND_ASSIGN(FakeHardware);
 };
diff --git a/common/hardware_interface.h b/common/hardware_interface.h
index 316ad3d..c9e2f85 100644
--- a/common/hardware_interface.h
+++ b/common/hardware_interface.h
@@ -17,6 +17,8 @@
 #ifndef UPDATE_ENGINE_COMMON_HARDWARE_INTERFACE_H_
 #define UPDATE_ENGINE_COMMON_HARDWARE_INTERFACE_H_
 
+#include <stdint.h>
+
 #include <string>
 #include <vector>
 
@@ -89,6 +91,9 @@
   // powerwash cycles. In case of an error, such as no directory available,
   // returns false.
   virtual bool GetPowerwashSafeDirectory(base::FilePath* path) const = 0;
+
+  // Returns the timestamp of the current OS build.
+  virtual int64_t GetBuildTimestamp() const = 0;
 };
 
 }  // namespace chromeos_update_engine