diff --git a/quic/core/http/http_constants.h b/quic/core/http/http_constants.h
index 17afe1b..285d379 100644
--- a/quic/core/http/http_constants.h
+++ b/quic/core/http/http_constants.h
@@ -42,6 +42,7 @@
 // SETTINGS_QPACK_BLOCKED_STREAMS.
 const uint64_t kDefaultMaximumBlockedStreams = 100;
 
+const char kUserAgentHeaderName[] = "user-agent";
 }  // namespace quic
 
 #endif  // QUICHE_QUIC_CORE_HTTP_HTTP_CONSTANTS_H_