diff --git a/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt b/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt
index 4aaa566eb852f..3b9060ad0ac3f 100644
--- a/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt
+++ b/packages/SystemUI/src/com/android/keyguard/ClockEventController.kt
@@ -259,7 +259,7 @@ constructor(
                 largeTimeListener?.update(shouldTimeListenerRun)
             }
 
-            override fun onTimeFormatChanged(timeFormat: String) {
+            override fun onTimeFormatChanged(timeFormat: String?) {
                 clock?.events?.onTimeFormatChanged(DateFormat.is24HourFormat(context))
             }