diff --git a/api/test/metrics/proto/metric.proto b/api/test/metrics/proto/metric.proto
index cdd312589d..94921a57cb 100644
--- a/api/test/metrics/proto/metric.proto
+++ b/api/test/metrics/proto/metric.proto
@@ -15,6 +15,8 @@ package webrtc.test_metrics;
 // Root message of the proto file. Contains collection of all the metrics.
 message MetricsSet {
   repeated Metric metrics = 1;
+  // Metadata associated with the whole metrics set.
+  map<string, string> metadata = 2;
 }
 
 enum Unit {