diff --git a/common/constants.cc b/common/constants.cc
index 0ac22f3..324bdc5 100644
--- a/common/constants.cc
+++ b/common/constants.cc
@@ -93,5 +93,6 @@
 const char kPayloadPropertyAuthorization[] = "AUTHORIZATION";
 const char kPayloadPropertyUserAgent[] = "USER_AGENT";
 const char kPayloadPropertyPowerwash[] = "POWERWASH";
+const char kPayloadPropertyNetworkId[] = "NETWORK_ID";
 
 }  // namespace chromeos_update_engine
diff --git a/common/constants.h b/common/constants.h
index 649034e..ab66921 100644
--- a/common/constants.h
+++ b/common/constants.h
@@ -94,6 +94,7 @@
 extern const char kPayloadPropertyAuthorization[];
 extern const char kPayloadPropertyUserAgent[];
 extern const char kPayloadPropertyPowerwash[];
+extern const char kPayloadPropertyNetworkId[];
 
 // A download source is any combination of protocol and server (that's of
 // interest to us when looking at UMA metrics) using which we may download