diff --git a/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc b/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
index d5bd97d459..c9163a15d8 100644
--- a/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
+++ b/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.cc
@@ -85,12 +85,12 @@ void NetEqReplacementInput::ReplacePacket() {
   rtc::Optional<RTPHeader> next_hdr = source_->NextHeader();
   RTC_DCHECK(next_hdr);
   uint8_t payload[12];
-  uint32_t input_frame_size_timestamps =
-      next_hdr->timestamp - packet_->header.header.timestamp;
-  if (next_hdr->sequenceNumber != packet_->header.header.sequenceNumber + 1) {
-    // Gap in packet sequence. Cannot estimate payload length based on timestamp
-    // difference.
-    input_frame_size_timestamps = 0;
+  uint32_t input_frame_size_timestamps = last_frame_size_timestamps_;
+  if (next_hdr->sequenceNumber == packet_->header.header.sequenceNumber + 1) {
+    // Packets are in order.
+    input_frame_size_timestamps =
+        next_hdr->timestamp - packet_->header.header.timestamp;
+    last_frame_size_timestamps_ = input_frame_size_timestamps;
   }
   FakeDecodeFromFile::PrepareEncoded(packet_->header.header.timestamp,
                                      input_frame_size_timestamps,
diff --git a/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.h b/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.h
index 07153dbb76..ee1e4ae66e 100644
--- a/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.h
+++ b/webrtc/modules/audio_coding/neteq/tools/neteq_replacement_input.h
@@ -11,6 +11,7 @@
 #ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_TOOLS_NETEQ_REPLACEMENT_INPUT_H_
 #define WEBRTC_MODULES_AUDIO_CODING_NETEQ_TOOLS_NETEQ_REPLACEMENT_INPUT_H_
 
+#include <memory>
 #include <set>
 
 #include "webrtc/modules/audio_coding/neteq/tools/neteq_input.h"
@@ -42,6 +43,7 @@ class NetEqReplacementInput : public NetEqInput {
   const std::set<uint8_t> comfort_noise_types_;
   const std::set<uint8_t> forbidden_types_;
   std::unique_ptr<PacketData> packet_;  // The next packet to deliver.
+  uint32_t last_frame_size_timestamps_ = 960;  // Initial guess: 20 ms @ 48 kHz.
 };
 
 }  // namespace test