diff --git a/quic/core/quic_sent_packet_manager.cc b/quic/core/quic_sent_packet_manager.cc
index 21dbc14..865cf3f 100644
--- a/quic/core/quic_sent_packet_manager.cc
+++ b/quic/core/quic_sent_packet_manager.cc
@@ -271,7 +271,8 @@
   send_algorithm_->AdjustNetworkParameters(bandwidth, rtt);
   if (debug_delegate_ != nullptr) {
     debug_delegate_->OnAdjustNetworkParameters(
-        bandwidth, rtt, old_cwnd, send_algorithm_->GetCongestionWindow());
+        bandwidth, rtt.IsZero() ? rtt_stats_.SmoothedOrInitialRtt() : rtt,
+        old_cwnd, send_algorithm_->GetCongestionWindow());
   }
 }