diff --git a/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h b/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
index 364d971837..73571b8dc2 100644
--- a/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
+++ b/webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h
@@ -278,6 +278,8 @@ struct PacketInfo {
         payload_size(payload_size),
         probe_cluster_id(probe_cluster_id) {}
 
+  static constexpr int kNotAProbe = -1;
+
   // Time corresponding to when this object was created.
   int64_t creation_time_ms;
   // Time corresponding to when the packet was received. Timestamped with the