diff --git a/quiche/quic/core/http/end_to_end_test.cc b/quiche/quic/core/http/end_to_end_test.cc
index 61e9d39..d65fec5 100644
--- a/quiche/quic/core/http/end_to_end_test.cc
+++ b/quiche/quic/core/http/end_to_end_test.cc
@@ -3068,7 +3068,11 @@
   {
     QuicConnection::ScopedPacketFlusher flusher(client_connection);
     if (client_connection->SupportsMultiplePacketNumberSpaces()) {
-      client_connection->SendAllPendingAcks();
+      if (client_connection->received_packet_manager()
+              .GetEarliestAckTimeout()
+              .IsInitialized()) {
+        client_connection->SendAllPendingAcks();
+      }
     } else {
       client_connection->SendAck();
     }