diff --git a/constants.h b/constants.h
index 1e69df8..5fbfa06 100644
--- a/constants.h
+++ b/constants.h
@@ -34,6 +34,7 @@
 extern const char kPrefsCurrentResponseSignature[];
 extern const char kPrefsCurrentUrlFailureCount[];
 extern const char kPrefsCurrentUrlIndex[];
+extern const char kPrefsDailyMetricsLastReportedAt[];
 extern const char kPrefsDeltaUpdateFailures[];
 extern const char kPrefsFullPayloadAttemptNumber[];
 extern const char kPrefsLastActivePingDay[];