diff --git a/modules/audio_processing/include/audio_processing_statistics.h b/modules/audio_processing/include/audio_processing_statistics.h
index 83c9d9932f..05c59054b3 100644
--- a/modules/audio_processing/include/audio_processing_statistics.h
+++ b/modules/audio_processing/include/audio_processing_statistics.h
@@ -48,7 +48,7 @@ struct AudioProcessingStats {
   // The instantaneous delay estimate produced in the AEC. The unit is in
   // milliseconds and the value is the instantaneous value at the time of the
   // call to |GetStatistics()|.
-  int delay_ms;
+  rtc::Optional<int32_t> delay_ms;
 };
 
 }  // namespace webrtc