diff --git a/quiche/quic/core/quic_connection_test.cc b/quiche/quic/core/quic_connection_test.cc
index 04e9d0e..bcb09f9 100644
--- a/quiche/quic/core/quic_connection_test.cc
+++ b/quiche/quic/core/quic_connection_test.cc
@@ -1058,7 +1058,7 @@
                                      QuicStreamOffset offset,
                                      StreamSendingState state,
                                      QuicPacketNumber* last_packet) {
-    QuicByteCount packet_size;
+    QuicByteCount packet_size = 0;
     // Save the last packet's size.
     EXPECT_CALL(*send_algorithm_, OnPacketSent(_, _, _, _, _))
         .Times(AnyNumber())