diff --git a/quic/core/quic_connection.cc b/quic/core/quic_connection.cc
index bbdaf9b..02a903b 100644
--- a/quic/core/quic_connection.cc
+++ b/quic/core/quic_connection.cc
@@ -5339,6 +5339,15 @@
         << "EffectivePeerMigration started without address change.";
     return;
   }
+  if (packet_creator_.HasPendingFrames()) {
+    QUIC_BUG(bug_731_2)
+        << "Starts effective peer migration with pending frame types: "
+        << packet_creator_.GetPendingFramesInfo() << ". Address change type is "
+        << AddressChangeTypeToString(type)
+        << ". Current frame type: " << framer_.current_received_frame_type()
+        << ". Previous frame type: "
+        << framer_.previously_received_frame_type();
+  }
 
   // Action items:
   //   1. Switch congestion controller;
@@ -5396,6 +5405,15 @@
   }
 
   // Update to the new peer address.
+  if (packet_creator_.HasPendingFrames()) {
+    QUIC_BUG(bug_731_1)
+        << "Starts effective peer migration with pending frame types: "
+        << packet_creator_.GetPendingFramesInfo() << ". Address change type is "
+        << AddressChangeTypeToString(type)
+        << ". Current frame type: " << framer_.current_received_frame_type()
+        << ". Previous frame type: "
+        << framer_.previously_received_frame_type();
+  }
   UpdatePeerAddress(last_received_packet_info_.source_address);
   // Update the default path.
   if (IsAlternativePath(last_received_packet_info_.destination_address,
diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index bc10b50..24b2be8 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -398,8 +398,7 @@
 }  // namespace
 
 QuicFramer::QuicFramer(const ParsedQuicVersionVector& supported_versions,
-                       QuicTime creation_time,
-                       Perspective perspective,
+                       QuicTime creation_time, Perspective perspective,
                        uint8_t expected_server_connection_id_length)
     : visitor_(nullptr),
       error_(QUIC_NO_ERROR),
@@ -429,7 +428,8 @@
       last_written_packet_number_length_(0),
       peer_ack_delay_exponent_(kDefaultAckDelayExponent),
       local_ack_delay_exponent_(kDefaultAckDelayExponent),
-      current_received_frame_type_(0) {
+      current_received_frame_type_(0),
+      previously_received_frame_type_(0) {
   QUICHE_DCHECK(!supported_versions.empty());
   version_ = supported_versions_[0];
   QUICHE_DCHECK(version_.IsKnown())
@@ -1964,8 +1964,10 @@
   // Handle the payload.
   if (VersionHasIetfQuicFrames(version_.transport_version)) {
     current_received_frame_type_ = 0;
+    previously_received_frame_type_ = 0;
     if (!ProcessIetfFrameData(&reader, *header, decrypted_level)) {
       current_received_frame_type_ = 0;
+      previously_received_frame_type_ = 0;
       QUICHE_DCHECK_NE(QUIC_NO_ERROR,
                        error_);  // ProcessIetfFrameData sets the error.
       QUICHE_DCHECK_NE("", detailed_error_);
@@ -1974,6 +1976,7 @@
       return false;
     }
     current_received_frame_type_ = 0;
+    previously_received_frame_type_ = 0;
   } else {
     if (!ProcessFrameData(&reader, *header)) {
       QUICHE_DCHECK_NE(QUIC_NO_ERROR,
@@ -3215,6 +3218,7 @@
           EncryptionLevelToString(decrypted_level)));
       return RaiseError(IETF_QUIC_PROTOCOL_VIOLATION);
     }
+    previously_received_frame_type_ = current_received_frame_type_;
     current_received_frame_type_ = frame_type;
 
     // Is now the number of bytes into which the frame type was encoded.
diff --git a/quic/core/quic_framer.h b/quic/core/quic_framer.h
index 2920db3..31cc756 100644
--- a/quic/core/quic_framer.h
+++ b/quic/core/quic_framer.h
@@ -650,6 +650,10 @@
     return current_received_frame_type_;
   }
 
+  uint64_t previously_received_frame_type() const {
+    return previously_received_frame_type_;
+  }
+
   // The connection ID length the framer expects on incoming IETF short headers
   // on the server.
   uint8_t GetExpectedServerConnectionIdLength() {
@@ -1190,6 +1194,11 @@
   // the Transport Connection Close when there is an error during frame
   // processing.
   uint64_t current_received_frame_type_;
+
+  // TODO(haoyuewang) Remove this debug utility.
+  // The type of the IETF frame preceding the frame currently being processed. 0
+  // when not processing a frame or only 1 frame has been processed.
+  uint64_t previously_received_frame_type_;
 };
 
 // Look for and parse the error code from the "<quic_error_code>:" text that
diff --git a/quic/core/quic_packet_creator.cc b/quic/core/quic_packet_creator.cc
index 3be1067..94cf48a 100644
--- a/quic/core/quic_packet_creator.cc
+++ b/quic/core/quic_packet_creator.cc
@@ -697,6 +697,10 @@
   return !queued_frames_.empty();
 }
 
+std::string QuicPacketCreator::GetPendingFramesInfo() const {
+  return QuicFramesToString(queued_frames_);
+}
+
 bool QuicPacketCreator::HasPendingRetransmittableFrames() const {
   return !packet_.retransmittable_frames.empty();
 }
diff --git a/quic/core/quic_packet_creator.h b/quic/core/quic_packet_creator.h
index abf24f6..9cc4bca 100644
--- a/quic/core/quic_packet_creator.h
+++ b/quic/core/quic_packet_creator.h
@@ -205,6 +205,10 @@
   // Returns true if there are frames pending to be serialized.
   bool HasPendingFrames() const;
 
+  // TODO(haoyuewang) Remove this debug utility.
+  // Returns the information of pending frames as a string.
+  std::string GetPendingFramesInfo() const;
+
   // Returns true if there are retransmittable frames pending to be serialized.
   bool HasPendingRetransmittableFrames() const;
 
diff --git a/quic/core/quic_packet_creator_test.cc b/quic/core/quic_packet_creator_test.cc
index a4e7a0a..3dc1a4b 100644
--- a/quic/core/quic_packet_creator_test.cc
+++ b/quic/core/quic_packet_creator_test.cc
@@ -423,6 +423,8 @@
   EXPECT_EQ(0u, consumed);
   CheckStreamFrame(frame, stream_id, std::string(), 0u, true);
   EXPECT_TRUE(creator_.HasPendingFrames());
+  EXPECT_TRUE(absl::StartsWith(creator_.GetPendingFramesInfo(),
+                               "type { STREAM_FRAME }"));
 }
 
 TEST_P(QuicPacketCreatorTest, CreateAllFreeBytesForStreamFrames) {