diff --git a/vpx_rtp/received_rtp_stream_statistics.py b/vpx_rtp/received_rtp_stream_statistics.py
index a287d3d..1cdd18f 100644
--- a/vpx_rtp/received_rtp_stream_statistics.py
+++ b/vpx_rtp/received_rtp_stream_statistics.py
@@ -1,3 +1,6 @@
+import time
+from typing import Optional
+
 from vpx_rtp.codecs.vpx import VIDEO_CLOCK_RATE
 from vpx_rtp.rtp import RtpPacket