diff --git a/quic/test_tools/quic_spdy_session_peer.cc b/quic/test_tools/quic_spdy_session_peer.cc
index d41ddfd..aee5d12 100644
--- a/quic/test_tools/quic_spdy_session_peer.cc
+++ b/quic/test_tools/quic_spdy_session_peer.cc
@@ -7,7 +7,9 @@
 #include "quic/core/http/quic_spdy_session.h"
 #include "quic/core/qpack/qpack_receive_stream.h"
 #include "quic/core/quic_utils.h"
+#include "quic/platform/api/quic_flags.h"
 #include "quic/test_tools/quic_session_peer.h"
+#include "common/platform/api/quiche_logging.h"
 
 namespace quic {
 namespace test {
@@ -115,5 +117,13 @@
   session->h3_datagram_supported_ = h3_datagram_supported;
 }
 
+// static
+void QuicSpdySessionPeer::EnableWebTransport(QuicSpdySession& session) {
+  SetQuicReloadableFlag(quic_h3_datagram, true);
+  QUICHE_DCHECK(session.WillNegotiateWebTransport());
+  session.h3_datagram_supported_ = true;
+  session.peer_supports_webtransport_ = true;
+}
+
 }  // namespace test
 }  // namespace quic