diff --git a/prefs_interface.h b/prefs_interface.h
index 7bc56ca..14962dd 100644
--- a/prefs_interface.h
+++ b/prefs_interface.h
@@ -28,9 +28,10 @@
 extern const char kPrefsWallClockWaitPeriod[];
 extern const char kPrefsUpdateFirstSeenAt[];
 extern const char kPrefsPayloadAttemptNumber[];
-extern const char kPrefsCurrentResponse[];
+extern const char kPrefsCurrentResponseSignature[];
 extern const char kPrefsCurrentUrlIndex[];
 extern const char kPrefsCurrentUrlFailureCount[];
+extern const char kPrefsBackoffExpiryTime[];
 
 // The prefs interface allows access to a persistent preferences
 // store. The two reasons for providing this as an interface are