diff --git a/platform_constants.h b/platform_constants.h
index 9f8778e..0c832c9 100644
--- a/platform_constants.h
+++ b/platform_constants.h
@@ -33,6 +33,11 @@
 // The name of the platform as sent to Omaha.
 extern const char kOmahaPlatformName[];
 
+// Path to the location of the public half of the payload key. The payload key
+// is used to sign the contents of the payload binary file: the manifest and the
+// whole payload.
+extern const char kUpdatePayloadPublicKeyPath[];
+
 }  // namespace constants
 }  // namespace chromeos_update_engine