diff --git a/quic/test_tools/simple_session_notifier.cc b/quic/test_tools/simple_session_notifier.cc
index c6e3801..624e4f7 100644
--- a/quic/test_tools/simple_session_notifier.cc
+++ b/quic/test_tools/simple_session_notifier.cc
@@ -434,6 +434,14 @@
   return !bytes_to_ack.Empty();
 }
 
+bool SimpleSessionNotifier::HasUnackedStreamData() const {
+  for (auto it : stream_map_) {
+    if (StreamIsWaitingForAcks(it.first))
+      return true;
+  }
+  return false;
+}
+
 bool SimpleSessionNotifier::OnControlFrameAcked(const QuicFrame& frame) {
   QuicControlFrameId id = GetControlFrameId(frame);
   if (id == kInvalidControlFrameId) {