diff --git a/gtfs-realtime/proto/gtfs-realtime.proto b/gtfs-realtime/proto/gtfs-realtime.proto
index bcd7d8823..c24743d84 100644
--- a/gtfs-realtime/proto/gtfs-realtime.proto
+++ b/gtfs-realtime/proto/gtfs-realtime.proto
@@ -73,6 +73,11 @@ message FeedHeader {
   // January 1st 1970 00:00:00 UTC).
   optional uint64 timestamp = 3;
 
+  // String that matches the feed_info.feed_version from the GTFS feed that the real
+  // time data is based on. Consumers can use this to identify which GTFS feed is
+  // currently active or when a new one is available to download.
+  optional string feed_version = 4;
+
   // The extensions namespace allows 3rd-party developers to extend the
   // GTFS Realtime specification in order to add and evaluate new features and
   // modifications to the spec.