diff --git a/http2/hpack/decoder/hpack_decoder.cc b/http2/hpack/decoder/hpack_decoder.cc
index b879511..6cfd1e0 100644
--- a/http2/hpack/decoder/hpack_decoder.cc
+++ b/http2/hpack/decoder/hpack_decoder.cc
@@ -60,7 +60,7 @@
   // which finally forwards them to the HpackDecoderListener.
   DecodeStatus status = block_decoder_.Decode(db);
   if (status == DecodeStatus::kDecodeError) {
-    ReportError(block_decoder_.error());
+    ReportError(block_decoder_.error(), "");
     HTTP2_CODE_COUNT_N(decompress_failure_3, 4, 23);
     return false;
   } else if (DetectError()) {
@@ -85,7 +85,7 @@
   }
   if (!block_decoder_.before_entry()) {
     // The HPACK block ended in the middle of an entry.
-    ReportError(HpackDecodingError::kTruncatedBlock);
+    ReportError(HpackDecodingError::kTruncatedBlock, "");
     HTTP2_CODE_COUNT_N(decompress_failure_3, 7, 23);
     return false;
   }
@@ -107,6 +107,7 @@
     HTTP2_DVLOG(2) << "Error detected in decoder_state_";
     HTTP2_CODE_COUNT_N(decompress_failure_3, 10, 23);
     error_ = decoder_state_.error();
+    detailed_error_ = decoder_state_.detailed_error();
   }
 
   return error_ != HpackDecodingError::kOk;
@@ -116,12 +117,14 @@
   return Http2EstimateMemoryUsage(entry_buffer_);
 }
 
-void HpackDecoder::ReportError(HpackDecodingError error) {
+void HpackDecoder::ReportError(HpackDecodingError error,
+                               std::string detailed_error) {
   HTTP2_DVLOG(3) << "HpackDecoder::ReportError is new="
                  << (error_ == HpackDecodingError::kOk ? "true" : "false")
                  << ", error: " << HpackDecodingErrorToString(error);
   if (error_ == HpackDecodingError::kOk) {
     error_ = error;
+    detailed_error_ = detailed_error;
     decoder_state_.listener()->OnHeaderErrorDetected(
         HpackDecodingErrorToString(error));
   }
diff --git a/http2/hpack/decoder/hpack_decoder.h b/http2/hpack/decoder/hpack_decoder.h
index efe334d..0666c38 100644
--- a/http2/hpack/decoder/hpack_decoder.h
+++ b/http2/hpack/decoder/hpack_decoder.h
@@ -103,11 +103,13 @@
   // Returns the estimate of dynamically allocated memory in bytes.
   size_t EstimateMemoryUsage() const;
 
+  std::string detailed_error() const { return detailed_error_; }
+
  private:
   friend class test::HpackDecoderPeer;
 
   // Reports an error to the listener IF this is the first error detected.
-  void ReportError(HpackDecodingError error);
+  void ReportError(HpackDecodingError error, std::string detailed_error);
 
   // The decompressor state, as defined by HPACK (i.e. the static and dynamic
   // tables).
@@ -121,6 +123,7 @@
 
   // Error code if an error has occurred, HpackDecodingError::kOk otherwise.
   HpackDecodingError error_;
+  std::string detailed_error_;
 };
 
 }  // namespace http2
diff --git a/http2/hpack/decoder/hpack_decoder_state.cc b/http2/hpack/decoder/hpack_decoder_state.cc
index 09b64c0..eba3e66 100644
--- a/http2/hpack/decoder/hpack_decoder_state.cc
+++ b/http2/hpack/decoder/hpack_decoder_state.cc
@@ -85,7 +85,7 @@
     return;
   }
   if (require_dynamic_table_size_update_) {
-    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate);
+    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate, "");
     return;
   }
   allow_dynamic_table_size_update_ = false;
@@ -93,7 +93,7 @@
   if (entry != nullptr) {
     listener_->OnHeader(entry->name, entry->value);
   } else {
-    ReportError(HpackDecodingError::kInvalidIndex);
+    ReportError(HpackDecodingError::kInvalidIndex, "");
   }
 }
 
@@ -108,7 +108,7 @@
     return;
   }
   if (require_dynamic_table_size_update_) {
-    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate);
+    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate, "");
     return;
   }
   allow_dynamic_table_size_update_ = false;
@@ -120,7 +120,7 @@
       decoder_tables_.Insert(entry->name, value);
     }
   } else {
-    ReportError(HpackDecodingError::kInvalidNameIndex);
+    ReportError(HpackDecodingError::kInvalidNameIndex, "");
   }
 }
 
@@ -134,7 +134,7 @@
     return;
   }
   if (require_dynamic_table_size_update_) {
-    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate);
+    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate, "");
     return;
   }
   allow_dynamic_table_size_update_ = false;
@@ -159,14 +159,15 @@
   if (!allow_dynamic_table_size_update_) {
     // At most two dynamic table size updates allowed at the start, and not
     // after a header.
-    ReportError(HpackDecodingError::kDynamicTableSizeUpdateNotAllowed);
+    ReportError(HpackDecodingError::kDynamicTableSizeUpdateNotAllowed, "");
     return;
   }
   if (require_dynamic_table_size_update_) {
     // The new size must not be greater than the low water mark.
     if (size_limit > lowest_header_table_size_) {
-      ReportError(HpackDecodingError::
-                      kInitialDynamicTableSizeUpdateIsAboveLowWaterMark);
+      ReportError(
+          HpackDecodingError::kInitialDynamicTableSizeUpdateIsAboveLowWaterMark,
+          "");
       return;
     }
     require_dynamic_table_size_update_ = false;
@@ -174,7 +175,8 @@
     // The new size must not be greater than the final max header table size
     // that the peer acknowledged.
     ReportError(
-        HpackDecodingError::kDynamicTableSizeUpdateIsAboveAcknowledgedSetting);
+        HpackDecodingError::kDynamicTableSizeUpdateIsAboveAcknowledgedSetting,
+        "");
     return;
   }
   decoder_tables_.DynamicTableSizeUpdate(size_limit);
@@ -187,11 +189,12 @@
   lowest_header_table_size_ = final_header_table_size_;
 }
 
-void HpackDecoderState::OnHpackDecodeError(HpackDecodingError error) {
+void HpackDecoderState::OnHpackDecodeError(HpackDecodingError error,
+                                           std::string detailed_error) {
   HTTP2_DVLOG(2) << "HpackDecoderState::OnHpackDecodeError "
                  << HpackDecodingErrorToString(error);
   if (error_ == HpackDecodingError::kOk) {
-    ReportError(error);
+    ReportError(error, detailed_error);
   }
 }
 
@@ -203,19 +206,21 @@
   if (require_dynamic_table_size_update_) {
     // Apparently the HPACK block was empty, but we needed it to contain at
     // least 1 dynamic table size update.
-    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate);
+    ReportError(HpackDecodingError::kMissingDynamicTableSizeUpdate, "");
   } else {
     listener_->OnHeaderListEnd();
   }
 }
 
-void HpackDecoderState::ReportError(HpackDecodingError error) {
+void HpackDecoderState::ReportError(HpackDecodingError error,
+                                    std::string detailed_error) {
   HTTP2_DVLOG(2) << "HpackDecoderState::ReportError is new="
                  << (error_ == HpackDecodingError::kOk ? "true" : "false")
                  << ", error: " << HpackDecodingErrorToString(error);
   if (error_ == HpackDecodingError::kOk) {
     listener_->OnHeaderErrorDetected(HpackDecodingErrorToString(error));
     error_ = error;
+    detailed_error_ = detailed_error;
   }
 }
 
diff --git a/http2/hpack/decoder/hpack_decoder_state.h b/http2/hpack/decoder/hpack_decoder_state.h
index 0735f6a..3854a6c 100644
--- a/http2/hpack/decoder/hpack_decoder_state.h
+++ b/http2/hpack/decoder/hpack_decoder_state.h
@@ -77,7 +77,8 @@
                              HpackDecoderStringBuffer* name_buffer,
                              HpackDecoderStringBuffer* value_buffer) override;
   void OnDynamicTableSizeUpdate(size_t size) override;
-  void OnHpackDecodeError(HpackDecodingError error) override;
+  void OnHpackDecodeError(HpackDecodingError error,
+                          std::string detailed_error) override;
 
   // OnHeaderBlockEnd notifies this object that an entire HPACK block has been
   // decoded, which might have extended into CONTINUATION blocks.
@@ -91,11 +92,13 @@
     return decoder_tables_;
   }
 
+  std::string detailed_error() const { return detailed_error_; }
+
  private:
   friend class test::HpackDecoderStatePeer;
 
   // Reports an error to the listener IF this is the first error detected.
-  void ReportError(HpackDecodingError error);
+  void ReportError(HpackDecodingError error, std::string detailed_error);
 
   // The static and dynamic HPACK tables.
   HpackDecoderTables decoder_tables_;
@@ -123,6 +126,7 @@
 
   // Has an error already been detected and reported to the listener?
   HpackDecodingError error_;
+  std::string detailed_error_;
 };
 
 }  // namespace http2
diff --git a/http2/hpack/decoder/hpack_decoder_state_test.cc b/http2/hpack/decoder/hpack_decoder_state_test.cc
index 02abb55..41a8453 100644
--- a/http2/hpack/decoder/hpack_decoder_state_test.cc
+++ b/http2/hpack/decoder/hpack_decoder_state_test.cc
@@ -455,7 +455,7 @@
   decoder_state_.OnLiteralNameAndValue(HpackEntryType::kIndexedLiteralHeader,
                                        &name_buffer_, &value_buffer_);
   decoder_state_.OnHeaderBlockEnd();
-  decoder_state_.OnHpackDecodeError(HpackDecodingError::kIndexVarintError);
+  decoder_state_.OnHpackDecodeError(HpackDecodingError::kIndexVarintError, "");
 }
 
 // Confirm that required size updates are validated.
@@ -524,7 +524,7 @@
   SendStartAndVerifyCallback();
   EXPECT_CALL(listener_,
               OnHeaderErrorDetected(Eq("Name Huffman encoding error")));
-  decoder_state_.OnHpackDecodeError(HpackDecodingError::kNameHuffmanError);
+  decoder_state_.OnHpackDecodeError(HpackDecodingError::kNameHuffmanError, "");
 
   // Further decoded entries are ignored.
   decoder_state_.OnIndexedHeader(1);
@@ -536,7 +536,7 @@
   decoder_state_.OnLiteralNameAndValue(HpackEntryType::kIndexedLiteralHeader,
                                        &name_buffer_, &value_buffer_);
   decoder_state_.OnHeaderBlockEnd();
-  decoder_state_.OnHpackDecodeError(HpackDecodingError::kIndexVarintError);
+  decoder_state_.OnHpackDecodeError(HpackDecodingError::kIndexVarintError, "");
 }
 
 }  // namespace
diff --git a/http2/hpack/decoder/hpack_whole_entry_buffer.cc b/http2/hpack/decoder/hpack_whole_entry_buffer.cc
index da5613e..dc93d1e 100644
--- a/http2/hpack/decoder/hpack_whole_entry_buffer.cc
+++ b/http2/hpack/decoder/hpack_whole_entry_buffer.cc
@@ -9,6 +9,7 @@
 #include "net/third_party/quiche/src/http2/platform/api/http2_logging.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_macros.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_string_utils.h"
+#include "net/third_party/quiche/src/common/platform/api/quiche_str_cat.h"
 
 namespace http2 {
 
@@ -58,7 +59,7 @@
     if (len > max_string_size_bytes_) {
       HTTP2_DVLOG(1) << "Name length (" << len << ") is longer than permitted ("
                      << max_string_size_bytes_ << ")";
-      ReportError(HpackDecodingError::kNameTooLong);
+      ReportError(HpackDecodingError::kNameTooLong, "");
       HTTP2_CODE_COUNT_N(decompress_failure_3, 18, 23);
       return;
     }
@@ -72,7 +73,7 @@
                  << Http2HexDump(quiche::QuicheStringPiece(data, len));
   DCHECK_EQ(maybe_name_index_, 0u);
   if (!error_detected_ && !name_.OnData(data, len)) {
-    ReportError(HpackDecodingError::kNameHuffmanError);
+    ReportError(HpackDecodingError::kNameHuffmanError, "");
     HTTP2_CODE_COUNT_N(decompress_failure_3, 19, 23);
   }
 }
@@ -81,7 +82,7 @@
   HTTP2_DVLOG(2) << "HpackWholeEntryBuffer::OnNameEnd";
   DCHECK_EQ(maybe_name_index_, 0u);
   if (!error_detected_ && !name_.OnEnd()) {
-    ReportError(HpackDecodingError::kNameHuffmanError);
+    ReportError(HpackDecodingError::kNameHuffmanError, "");
     HTTP2_CODE_COUNT_N(decompress_failure_3, 20, 23);
   }
 }
@@ -91,10 +92,11 @@
                  << (huffman_encoded ? "true" : "false") << ",  len=" << len;
   if (!error_detected_) {
     if (len > max_string_size_bytes_) {
-      HTTP2_DVLOG(1) << "Value length (" << len
-                     << ") is longer than permitted (" << max_string_size_bytes_
-                     << ")";
-      ReportError(HpackDecodingError::kValueTooLong);
+      std::string detailed_error = quiche::QuicheStrCat(
+          "Value length (", len, ") of [", name_.str(),
+          "] is longer than permitted (", max_string_size_bytes_, ")");
+      HTTP2_DVLOG(1) << detailed_error;
+      ReportError(HpackDecodingError::kValueTooLong, detailed_error);
       HTTP2_CODE_COUNT_N(decompress_failure_3, 21, 23);
       return;
     }
@@ -107,7 +109,7 @@
                  << " data:\n"
                  << Http2HexDump(quiche::QuicheStringPiece(data, len));
   if (!error_detected_ && !value_.OnData(data, len)) {
-    ReportError(HpackDecodingError::kValueHuffmanError);
+    ReportError(HpackDecodingError::kValueHuffmanError, "");
     HTTP2_CODE_COUNT_N(decompress_failure_3, 22, 23);
   }
 }
@@ -118,7 +120,7 @@
     return;
   }
   if (!value_.OnEnd()) {
-    ReportError(HpackDecodingError::kValueHuffmanError);
+    ReportError(HpackDecodingError::kValueHuffmanError, "");
     HTTP2_CODE_COUNT_N(decompress_failure_3, 23, 23);
     return;
   }
@@ -138,12 +140,13 @@
   listener_->OnDynamicTableSizeUpdate(size);
 }
 
-void HpackWholeEntryBuffer::ReportError(HpackDecodingError error) {
+void HpackWholeEntryBuffer::ReportError(HpackDecodingError error,
+                                        std::string detailed_error) {
   if (!error_detected_) {
     HTTP2_DVLOG(1) << "HpackWholeEntryBuffer::ReportError: "
                    << HpackDecodingErrorToString(error);
     error_detected_ = true;
-    listener_->OnHpackDecodeError(error);
+    listener_->OnHpackDecodeError(error, detailed_error);
     listener_ = HpackWholeEntryNoOpListener::NoOpListener();
   }
 }
diff --git a/http2/hpack/decoder/hpack_whole_entry_buffer.h b/http2/hpack/decoder/hpack_whole_entry_buffer.h
index 5c0bfe2..afca3b8 100644
--- a/http2/hpack/decoder/hpack_whole_entry_buffer.h
+++ b/http2/hpack/decoder/hpack_whole_entry_buffer.h
@@ -80,7 +80,7 @@
   void OnDynamicTableSizeUpdate(size_t size) override;
 
  private:
-  void ReportError(HpackDecodingError error);
+  void ReportError(HpackDecodingError error, std::string detailed_error);
 
   HpackWholeEntryListener* listener_;
   HpackDecoderStringBuffer name_, value_;
diff --git a/http2/hpack/decoder/hpack_whole_entry_buffer_test.cc b/http2/hpack/decoder/hpack_whole_entry_buffer_test.cc
index a48afd7..2396bd6 100644
--- a/http2/hpack/decoder/hpack_whole_entry_buffer_test.cc
+++ b/http2/hpack/decoder/hpack_whole_entry_buffer_test.cc
@@ -11,6 +11,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "net/third_party/quiche/src/http2/platform/api/http2_test_helpers.h"
 
+using ::testing::_;
 using ::testing::AllOf;
 using ::testing::InSequence;
 using ::testing::Property;
@@ -26,17 +27,24 @@
  public:
   ~MockHpackWholeEntryListener() override = default;
 
-  MOCK_METHOD1(OnIndexedHeader, void(size_t index));
-  MOCK_METHOD3(OnNameIndexAndLiteralValue,
-               void(HpackEntryType entry_type,
-                    size_t name_index,
-                    HpackDecoderStringBuffer* value_buffer));
-  MOCK_METHOD3(OnLiteralNameAndValue,
-               void(HpackEntryType entry_type,
-                    HpackDecoderStringBuffer* name_buffer,
-                    HpackDecoderStringBuffer* value_buffer));
-  MOCK_METHOD1(OnDynamicTableSizeUpdate, void(size_t size));
-  MOCK_METHOD1(OnHpackDecodeError, void(HpackDecodingError error));
+  MOCK_METHOD(void, OnIndexedHeader, (size_t index), (override));
+  MOCK_METHOD(void,
+              OnNameIndexAndLiteralValue,
+              (HpackEntryType entry_type,
+               size_t name_index,
+               HpackDecoderStringBuffer* value_buffer),
+              (override));
+  MOCK_METHOD(void,
+              OnLiteralNameAndValue,
+              (HpackEntryType entry_type,
+               HpackDecoderStringBuffer* name_buffer,
+               HpackDecoderStringBuffer* value_buffer),
+              (override));
+  MOCK_METHOD(void, OnDynamicTableSizeUpdate, (size_t size), (override));
+  MOCK_METHOD(void,
+              OnHpackDecodeError,
+              (HpackDecodingError error, std::string detailed_error),
+              (override));
 };
 
 class HpackWholeEntryBufferTest : public ::testing::Test {
@@ -154,14 +162,21 @@
 // Verify that a name longer than the allowed size generates an error.
 TEST_F(HpackWholeEntryBufferTest, NameTooLong) {
   entry_buffer_.OnStartLiteralHeader(HpackEntryType::kIndexedLiteralHeader, 0);
-  EXPECT_CALL(listener_, OnHpackDecodeError(HpackDecodingError::kNameTooLong));
+  EXPECT_CALL(listener_,
+              OnHpackDecodeError(HpackDecodingError::kNameTooLong, _));
   entry_buffer_.OnNameStart(false, kMaxStringSize + 1);
 }
 
-// Verify that a name longer than the allowed size generates an error.
+// Verify that a value longer than the allowed size generates an error.
 TEST_F(HpackWholeEntryBufferTest, ValueTooLong) {
-  entry_buffer_.OnStartLiteralHeader(HpackEntryType::kIndexedLiteralHeader, 1);
-  EXPECT_CALL(listener_, OnHpackDecodeError(HpackDecodingError::kValueTooLong));
+  entry_buffer_.OnStartLiteralHeader(HpackEntryType::kIndexedLiteralHeader, 0);
+  EXPECT_CALL(listener_,
+              OnHpackDecodeError(
+                  HpackDecodingError::kValueTooLong,
+                  "Value length (21) of [path] is longer than permitted (20)"));
+  entry_buffer_.OnNameStart(false, 4);
+  entry_buffer_.OnNameData("path", 4);
+  entry_buffer_.OnNameEnd();
   entry_buffer_.OnValueStart(false, kMaxStringSize + 1);
 }
 
@@ -175,7 +190,7 @@
   entry_buffer_.OnNameData(data, 3);
 
   EXPECT_CALL(listener_,
-              OnHpackDecodeError(HpackDecodingError::kNameHuffmanError));
+              OnHpackDecodeError(HpackDecodingError::kNameHuffmanError, _));
 
   entry_buffer_.OnNameData(data, 1);
 
@@ -194,7 +209,7 @@
   entry_buffer_.OnValueData(data, 3);
 
   EXPECT_CALL(listener_,
-              OnHpackDecodeError(HpackDecodingError::kValueHuffmanError));
+              OnHpackDecodeError(HpackDecodingError::kValueHuffmanError, _));
 
   entry_buffer_.OnValueEnd();
 
diff --git a/http2/hpack/decoder/hpack_whole_entry_listener.cc b/http2/hpack/decoder/hpack_whole_entry_listener.cc
index 02f3a7a..5900b6d 100644
--- a/http2/hpack/decoder/hpack_whole_entry_listener.cc
+++ b/http2/hpack/decoder/hpack_whole_entry_listener.cc
@@ -21,7 +21,8 @@
     HpackDecoderStringBuffer* /*value_buffer*/) {}
 void HpackWholeEntryNoOpListener::OnDynamicTableSizeUpdate(size_t /*size*/) {}
 void HpackWholeEntryNoOpListener::OnHpackDecodeError(
-    HpackDecodingError /*error*/) {}
+    HpackDecodingError /*error*/,
+    std::string /*detailed_error*/) {}
 
 // static
 HpackWholeEntryNoOpListener* HpackWholeEntryNoOpListener::NoOpListener() {
diff --git a/http2/hpack/decoder/hpack_whole_entry_listener.h b/http2/hpack/decoder/hpack_whole_entry_listener.h
index ef2f77e..ec2ae52 100644
--- a/http2/hpack/decoder/hpack_whole_entry_listener.h
+++ b/http2/hpack/decoder/hpack_whole_entry_listener.h
@@ -51,7 +51,8 @@
   virtual void OnDynamicTableSizeUpdate(size_t size) = 0;
 
   // OnHpackDecodeError is called if an error is detected while decoding.
-  virtual void OnHpackDecodeError(HpackDecodingError error) = 0;
+  virtual void OnHpackDecodeError(HpackDecodingError error,
+                                  std::string detailed_error) = 0;
 };
 
 // A no-op implementation of HpackWholeEntryDecoderListener, useful for ignoring
@@ -69,7 +70,8 @@
                              HpackDecoderStringBuffer* name_buffer,
                              HpackDecoderStringBuffer* value_buffer) override;
   void OnDynamicTableSizeUpdate(size_t size) override;
-  void OnHpackDecodeError(HpackDecodingError error) override;
+  void OnHpackDecodeError(HpackDecodingError error,
+                          std::string detailed_error) override;
 
   // Returns a listener that ignores all the calls.
   static HpackWholeEntryNoOpListener* NoOpListener();