diff --git a/prefs_interface.h b/prefs_interface.h
index 3cb4059..d0ff0d0 100644
--- a/prefs_interface.h
+++ b/prefs_interface.h
@@ -26,6 +26,7 @@
 extern const char kPrefsUpdateStateSignedSHA256Context[];
 extern const char kPrefsUpdateCheckCount[];
 extern const char kPrefsWallClockWaitPeriod[];
+extern const char kPrefsUpdateFirstSeenAt[];
 
 // The prefs interface allows access to a persistent preferences
 // store. The two reasons for providing this as an interface are