diff --git a/webrtc/video_engine/report_block_stats.cc b/webrtc/video_engine/report_block_stats.cc
index 61167f167c..ea18e830e3 100644
--- a/webrtc/video_engine/report_block_stats.cc
+++ b/webrtc/video_engine/report_block_stats.cc
@@ -100,6 +100,9 @@ void ReportBlockStats::StoreAndAddPacketIncrement(
 }
 
 int ReportBlockStats::FractionLostInPercent() const {
+  if (num_sequence_numbers_ == 0) {
+    return -1;
+  }
   return FractionLost(
       num_lost_sequence_numbers_, num_sequence_numbers_) * 100 / 255;
 }
diff --git a/webrtc/video_engine/report_block_stats.h b/webrtc/video_engine/report_block_stats.h
index 2d6b16e657..dadcc9d410 100644
--- a/webrtc/video_engine/report_block_stats.h
+++ b/webrtc/video_engine/report_block_stats.h
@@ -36,7 +36,8 @@ class ReportBlockStats {
              uint32_t remote_ssrc,
              uint32_t source_ssrc);
 
-  // Returns the total fraction of lost packets.
+  // Returns the total fraction of lost packets (or -1 if less than two report
+  // blocks have been stored).
   int FractionLostInPercent() const;
 
  private:
diff --git a/webrtc/video_engine/report_block_stats_unittest.cc b/webrtc/video_engine/report_block_stats_unittest.cc
index 10c4104241..e688d2eb01 100644
--- a/webrtc/video_engine/report_block_stats_unittest.cc
+++ b/webrtc/video_engine/report_block_stats_unittest.cc
@@ -129,11 +129,11 @@ TEST_F(ReportBlockStatsTest, AggregateAndStore_TwoSsrcs) {
 TEST_F(ReportBlockStatsTest, StoreAndGetFractionLost) {
   const uint32_t kRemoteSsrc = 1;
   ReportBlockStats stats;
-  EXPECT_EQ(0, stats.FractionLostInPercent());
+  EXPECT_EQ(-1, stats.FractionLostInPercent());
 
-  // First block => 0%
+  // First block.
   stats.Store(RtcpReportBlockToRtcpStatistics(block1_1_), kRemoteSsrc, kSsrc1);
-  EXPECT_EQ(0, stats.FractionLostInPercent());
+  EXPECT_EQ(-1, stats.FractionLostInPercent());
   // fl: 100 * (15-10) / (24100-24000) = 5%
   stats.Store(RtcpReportBlockToRtcpStatistics(block1_2_), kRemoteSsrc, kSsrc1);
   EXPECT_EQ(5, stats.FractionLostInPercent());
diff --git a/webrtc/video_engine/vie_channel.cc b/webrtc/video_engine/vie_channel.cc
index ee560b42c8..a83e30fc8c 100644
--- a/webrtc/video_engine/vie_channel.cc
+++ b/webrtc/video_engine/vie_channel.cc
@@ -212,8 +212,11 @@ void ViEChannel::UpdateHistograms() {
             "WebRTC.Video.UniqueNackRequestsReceivedInPercent",
                 rtcp_received.UniqueNackRequestsInPercent());
       }
-      RTC_HISTOGRAM_PERCENTAGE("WebRTC.Video.SentPacketsLostInPercent",
-          report_block_stats_sender_->FractionLostInPercent());
+      int fraction_lost = report_block_stats_sender_->FractionLostInPercent();
+      if (fraction_lost != -1) {
+        RTC_HISTOGRAM_PERCENTAGE("WebRTC.Video.SentPacketsLostInPercent",
+            fraction_lost);
+      }
     }
   } else if (vie_receiver_.GetRemoteSsrc() > 0) {
     // Get receive stats if we are receiving packets, i.e. there is a remote
@@ -230,8 +233,11 @@ void ViEChannel::UpdateHistograms() {
         RTC_HISTOGRAM_PERCENTAGE("WebRTC.Video.UniqueNackRequestsSentInPercent",
             rtcp_sent.UniqueNackRequestsInPercent());
       }
-      RTC_HISTOGRAM_PERCENTAGE("WebRTC.Video.ReceivedPacketsLostInPercent",
-          report_block_stats_receiver_->FractionLostInPercent());
+      int fraction_lost = report_block_stats_receiver_->FractionLostInPercent();
+      if (fraction_lost != -1) {
+        RTC_HISTOGRAM_PERCENTAGE("WebRTC.Video.ReceivedPacketsLostInPercent",
+            fraction_lost);
+      }
     }
 
     StreamDataCounters rtp;