diff --git a/modules/rtp_rtcp/source/source_tracker.cc b/modules/rtp_rtcp/source/source_tracker.cc
index 4d1f40641f..17862148eb 100644
--- a/modules/rtp_rtcp/source/source_tracker.cc
+++ b/modules/rtp_rtcp/source/source_tracker.cc
@@ -94,6 +94,9 @@ SourceTracker::SourceEntry& SourceTracker::UpdateEntry(const SourceKey& key) {
 }
 
 void SourceTracker::PruneEntries(Timestamp now) const {
+  if (now < Timestamp::Zero() + kTimeout) {
+    return;
+  }
   Timestamp prune = now - kTimeout;
   while (!list_.empty() && list_.back().second.timestamp < prune) {
     map_.erase(list_.back().first);
diff --git a/modules/rtp_rtcp/source/source_tracker_unittest.cc b/modules/rtp_rtcp/source/source_tracker_unittest.cc
index 32ac711ca5..749bfbaa41 100644
--- a/modules/rtp_rtcp/source/source_tracker_unittest.cc
+++ b/modules/rtp_rtcp/source/source_tracker_unittest.cc
@@ -535,4 +535,12 @@ TEST(SourceTrackerTest, TimedOutSourcesAreRemoved) {
                                     kRtpTimestamp1, extensions1)));
 }
 
+TEST(SourceTrackerTest, AvoidNegativeTimestamp) {
+  SimulatedClock clock(Timestamp::Zero());
+  SourceTracker tracker(&clock);
+  tracker.OnFrameDelivered(RtpPacketInfos(
+      {RtpPacketInfo(/*ssrc=*/111, /*csrcs=*/{}, /*rtp_timestamp=*/0,
+                     /*receive_time=*/Timestamp::Zero())}));
+}
+
 }  // namespace webrtc