diff --git a/http2/adapter/callback_visitor.cc b/http2/adapter/callback_visitor.cc
index 3bc7784..7701cc6 100644
--- a/http2/adapter/callback_visitor.cc
+++ b/http2/adapter/callback_visitor.cc
@@ -120,7 +120,7 @@
   }
 }
 
-void CallbackVisitor::OnBeginHeadersForStream(Http2StreamId stream_id) {
+bool CallbackVisitor::OnBeginHeadersForStream(Http2StreamId stream_id) {
   auto it = GetStreamInfo(stream_id);
   if (it->second->received_headers) {
     // At least one headers frame has already been received.
@@ -142,12 +142,13 @@
         break;
     }
   }
+  it->second->received_headers = true;
   if (callbacks_->on_begin_headers_callback) {
     const int result = callbacks_->on_begin_headers_callback(
         nullptr, &current_frame_, user_data_);
-    QUICHE_DCHECK_EQ(0, result);
+    return result == 0;
   }
-  it->second->received_headers = true;
+  return true;
 }
 
 Http2VisitorInterface::OnHeaderResult CallbackVisitor::OnHeaderForStream(
diff --git a/http2/adapter/callback_visitor.h b/http2/adapter/callback_visitor.h
index 8a32862..5cf6304 100644
--- a/http2/adapter/callback_visitor.h
+++ b/http2/adapter/callback_visitor.h
@@ -31,7 +31,7 @@
   void OnSetting(Http2Setting setting) override;
   void OnSettingsEnd() override;
   void OnSettingsAck() override;
-  void OnBeginHeadersForStream(Http2StreamId stream_id) override;
+  bool OnBeginHeadersForStream(Http2StreamId stream_id) override;
   OnHeaderResult OnHeaderForStream(Http2StreamId stream_id,
                                    absl::string_view name,
                                    absl::string_view value) override;
diff --git a/http2/adapter/http2_visitor_interface.h b/http2/adapter/http2_visitor_interface.h
index feaff14..292021a 100644
--- a/http2/adapter/http2_visitor_interface.h
+++ b/http2/adapter/http2_visitor_interface.h
@@ -77,8 +77,9 @@
   virtual void OnSettingsAck() = 0;
 
   // Called when the connection receives the header block for a HEADERS frame on
-  // a stream but has not yet parsed individual headers.
-  virtual void OnBeginHeadersForStream(Http2StreamId stream_id) = 0;
+  // a stream but has not yet parsed individual headers. Returns false if a
+  // fatal error has occurred.
+  virtual bool OnBeginHeadersForStream(Http2StreamId stream_id) = 0;
 
   // Called when the connection receives the header |key| and |value| for a
   // stream. The HTTP/2 pseudo-headers defined in RFC 7540 Sections 8.1.2.3 and
diff --git a/http2/adapter/mock_http2_visitor.h b/http2/adapter/mock_http2_visitor.h
index 264c34e..3daa805 100644
--- a/http2/adapter/mock_http2_visitor.h
+++ b/http2/adapter/mock_http2_visitor.h
@@ -13,6 +13,8 @@
 class QUICHE_NO_EXPORT MockHttp2Visitor : public Http2VisitorInterface {
  public:
   MockHttp2Visitor() {
+    ON_CALL(*this, OnBeginHeadersForStream)
+        .WillByDefault(testing::Return(true));
     ON_CALL(*this, OnHeaderForStream).WillByDefault(testing::Return(HEADER_OK));
     ON_CALL(*this, OnInvalidFrame).WillByDefault(testing::Return(true));
     ON_CALL(*this, OnMetadataEndForStream).WillByDefault(testing::Return(true));
@@ -32,9 +34,7 @@
   MOCK_METHOD(void, OnSetting, (Http2Setting setting), (override));
   MOCK_METHOD(void, OnSettingsEnd, (), (override));
   MOCK_METHOD(void, OnSettingsAck, (), (override));
-  MOCK_METHOD(void,
-              OnBeginHeadersForStream,
-              (Http2StreamId stream_id),
+  MOCK_METHOD(bool, OnBeginHeadersForStream, (Http2StreamId stream_id),
               (override));
 
   MOCK_METHOD(OnHeaderResult, OnHeaderForStream,
diff --git a/http2/adapter/nghttp2_adapter_test.cc b/http2/adapter/nghttp2_adapter_test.cc
index b9d9c1d..84f3939 100644
--- a/http2/adapter/nghttp2_adapter_test.cc
+++ b/http2/adapter/nghttp2_adapter_test.cc
@@ -636,6 +636,69 @@
   EXPECT_THAT(visitor.data(), EqualsFrames({spdy::SpdyFrameType::SETTINGS}));
 }
 
+TEST(NgHttp2AdapterTest, ClientRejectsHeaders) {
+  DataSavingVisitor visitor;
+  auto adapter = NgHttp2Adapter::CreateClientAdapter(visitor);
+
+  testing::InSequence s;
+
+  const std::vector<const Header> headers1 =
+      ToHeaders({{":method", "GET"},
+                 {":scheme", "http"},
+                 {":authority", "example.com"},
+                 {":path", "/this/is/request/one"}});
+
+  const char* kSentinel1 = "arbitrary pointer 1";
+  const int32_t stream_id1 =
+      adapter->SubmitRequest(headers1, nullptr, const_cast<char*>(kSentinel1));
+  ASSERT_GT(stream_id1, 0);
+  QUICHE_LOG(INFO) << "Created stream: " << stream_id1;
+
+  EXPECT_CALL(visitor, OnBeforeFrameSent(HEADERS, stream_id1, _, 0x5));
+  EXPECT_CALL(visitor, OnFrameSent(HEADERS, stream_id1, _, 0x5, 0));
+
+  int result = adapter->Send();
+  EXPECT_EQ(0, result);
+  absl::string_view data = visitor.data();
+  EXPECT_THAT(data, testing::StartsWith(spdy::kHttp2ConnectionHeaderPrefix));
+  data.remove_prefix(strlen(spdy::kHttp2ConnectionHeaderPrefix));
+  EXPECT_THAT(data, EqualsFrames({spdy::SpdyFrameType::HEADERS}));
+  visitor.Clear();
+
+  const std::string stream_frames =
+      TestFrameSequence()
+          .ServerPreface()
+          .Headers(1,
+                   {{":status", "200"},
+                    {"server", "my-fake-server"},
+                    {"date", "Tue, 6 Apr 2021 12:54:01 GMT"}},
+                   /*fin=*/false)
+          .Data(1, "This is the response body.")
+          .Serialize();
+
+  // Server preface (empty SETTINGS)
+  EXPECT_CALL(visitor, OnFrameHeader(0, 0, SETTINGS, 0));
+  EXPECT_CALL(visitor, OnSettingsStart());
+  EXPECT_CALL(visitor, OnSettingsEnd());
+
+  EXPECT_CALL(visitor, OnFrameHeader(1, _, HEADERS, 4));
+  EXPECT_CALL(visitor, OnBeginHeadersForStream(1))
+      .WillOnce(testing::Return(false));
+  // Rejecting headers leads to a connection error.
+  EXPECT_CALL(visitor, OnConnectionError());
+
+  const ssize_t stream_result = adapter->ProcessBytes(stream_frames);
+  EXPECT_EQ(NGHTTP2_ERR_CALLBACK_FAILURE, stream_result);
+
+  EXPECT_CALL(visitor, OnBeforeFrameSent(SETTINGS, 0, 0, 0x1));
+  EXPECT_CALL(visitor, OnFrameSent(SETTINGS, 0, 0, 0x1, 0));
+
+  EXPECT_TRUE(adapter->session().want_write());
+  result = adapter->Send();
+  EXPECT_EQ(0, result);
+  EXPECT_THAT(visitor.data(), EqualsFrames({spdy::SpdyFrameType::SETTINGS}));
+}
+
 TEST(NgHttp2AdapterTest, ClientSubmitRequest) {
   DataSavingVisitor visitor;
   auto adapter = NgHttp2Adapter::CreateClientAdapter(visitor);
diff --git a/http2/adapter/nghttp2_callbacks.cc b/http2/adapter/nghttp2_callbacks.cc
index f34cdf0..51b2054 100644
--- a/http2/adapter/nghttp2_callbacks.cc
+++ b/http2/adapter/nghttp2_callbacks.cc
@@ -148,8 +148,8 @@
                    void* user_data) {
   QUICHE_CHECK_NE(user_data, nullptr);
   auto* visitor = static_cast<Http2VisitorInterface*>(user_data);
-  visitor->OnBeginHeadersForStream(frame->hd.stream_id);
-  return 0;
+  const bool result = visitor->OnBeginHeadersForStream(frame->hd.stream_id);
+  return result ? 0 : NGHTTP2_ERR_CALLBACK_FAILURE;
 }
 
 int OnHeader(nghttp2_session* /* session */, const nghttp2_frame* frame,
diff --git a/http2/adapter/oghttp2_adapter_test.cc b/http2/adapter/oghttp2_adapter_test.cc
index 87576bb..b8b2a3d 100644
--- a/http2/adapter/oghttp2_adapter_test.cc
+++ b/http2/adapter/oghttp2_adapter_test.cc
@@ -297,7 +297,7 @@
                                             spdy::SpdyFrameType::RST_STREAM}));
 }
 
-TEST(NgHttp2AdapterTest, ClientConnectionErrorWhileHandlingHeaders) {
+TEST(OgHttp2AdapterClientTest, ClientConnectionErrorWhileHandlingHeaders) {
   DataSavingVisitor visitor;
   OgHttp2Adapter::Options options{.perspective = Perspective::kClient};
   auto adapter = OgHttp2Adapter::Create(visitor, options);
@@ -373,6 +373,78 @@
   EXPECT_THAT(visitor.data(), EqualsFrames({spdy::SpdyFrameType::SETTINGS}));
 }
 
+TEST(OgHttp2AdapterClientTest, ClientRejectsHeaders) {
+  DataSavingVisitor visitor;
+  OgHttp2Adapter::Options options{.perspective = Perspective::kClient};
+  auto adapter = OgHttp2Adapter::Create(visitor, options);
+
+  testing::InSequence s;
+
+  const std::vector<const Header> headers1 =
+      ToHeaders({{":method", "GET"},
+                 {":scheme", "http"},
+                 {":authority", "example.com"},
+                 {":path", "/this/is/request/one"}});
+
+  const char* kSentinel1 = "arbitrary pointer 1";
+  const int32_t stream_id1 =
+      adapter->SubmitRequest(headers1, nullptr, const_cast<char*>(kSentinel1));
+  ASSERT_GT(stream_id1, 0);
+  QUICHE_LOG(INFO) << "Created stream: " << stream_id1;
+
+  EXPECT_CALL(visitor, OnBeforeFrameSent(SETTINGS, 0, _, 0x0));
+  EXPECT_CALL(visitor, OnFrameSent(SETTINGS, 0, _, 0x0, 0));
+  EXPECT_CALL(visitor, OnBeforeFrameSent(HEADERS, stream_id1, _, 0x5));
+  EXPECT_CALL(visitor, OnFrameSent(HEADERS, stream_id1, _, 0x5, 0));
+
+  int result = adapter->Send();
+  EXPECT_EQ(0, result);
+  absl::string_view data = visitor.data();
+  EXPECT_THAT(data, testing::StartsWith(spdy::kHttp2ConnectionHeaderPrefix));
+  data.remove_prefix(strlen(spdy::kHttp2ConnectionHeaderPrefix));
+  EXPECT_THAT(data, EqualsFrames({spdy::SpdyFrameType::SETTINGS,
+                                  spdy::SpdyFrameType::HEADERS}));
+  visitor.Clear();
+
+  const std::string stream_frames =
+      TestFrameSequence()
+          .ServerPreface()
+          .Headers(1,
+                   {{":status", "200"},
+                    {"server", "my-fake-server"},
+                    {"date", "Tue, 6 Apr 2021 12:54:01 GMT"}},
+                   /*fin=*/false)
+          .Data(1, "This is the response body.")
+          .Serialize();
+
+  // Server preface (empty SETTINGS)
+  EXPECT_CALL(visitor, OnFrameHeader(0, 0, SETTINGS, 0));
+  EXPECT_CALL(visitor, OnSettingsStart());
+  EXPECT_CALL(visitor, OnSettingsEnd());
+
+  EXPECT_CALL(visitor, OnFrameHeader(1, _, HEADERS, 4));
+  EXPECT_CALL(visitor, OnBeginHeadersForStream(1))
+      .WillOnce(testing::Return(false));
+  // Rejecting headers leads to a connection error.
+  EXPECT_CALL(visitor, OnConnectionError());
+  // Note: OgHttp2Adapter continues processing bytes until the input is
+  // complete.
+  EXPECT_CALL(visitor, OnFrameHeader(1, _, DATA, 0));
+  EXPECT_CALL(visitor, OnBeginDataForStream(1, _));
+  EXPECT_CALL(visitor, OnDataForStream(1, "This is the response body."));
+
+  const ssize_t stream_result = adapter->ProcessBytes(stream_frames);
+  EXPECT_EQ(stream_result, stream_frames.size());
+
+  EXPECT_CALL(visitor, OnBeforeFrameSent(SETTINGS, 0, 0, 0x1));
+  EXPECT_CALL(visitor, OnFrameSent(SETTINGS, 0, 0, 0x1, 0));
+
+  EXPECT_TRUE(adapter->session().want_write());
+  result = adapter->Send();
+  EXPECT_EQ(0, result);
+  EXPECT_THAT(visitor.data(), EqualsFrames({spdy::SpdyFrameType::SETTINGS}));
+}
+
 // TODO(birenroy): Validate headers and re-enable this test. The library should
 // invoke OnErrorDebug() with an error message for the invalid header. The
 // library should also invoke OnInvalidFrame() for the invalid HEADERS frame.
diff --git a/http2/adapter/oghttp2_session.cc b/http2/adapter/oghttp2_session.cc
index 1dac781..93195f3 100644
--- a/http2/adapter/oghttp2_session.cc
+++ b/http2/adapter/oghttp2_session.cc
@@ -100,7 +100,10 @@
 }  // namespace
 
 void OgHttp2Session::PassthroughHeadersHandler::OnHeaderBlockStart() {
-  visitor_.OnBeginHeadersForStream(stream_id_);
+  const bool status = visitor_.OnBeginHeadersForStream(stream_id_);
+  if (!status) {
+    result_ = Http2VisitorInterface::HEADER_CONNECTION_ERROR;
+  }
 }
 
 void OgHttp2Session::PassthroughHeadersHandler::OnHeader(
diff --git a/http2/adapter/recording_http2_visitor.cc b/http2/adapter/recording_http2_visitor.cc
index 0706c5e..75f3749 100644
--- a/http2/adapter/recording_http2_visitor.cc
+++ b/http2/adapter/recording_http2_visitor.cc
@@ -41,8 +41,9 @@
   events_.push_back("OnSettingsAck");
 }
 
-void RecordingHttp2Visitor::OnBeginHeadersForStream(Http2StreamId stream_id) {
+bool RecordingHttp2Visitor::OnBeginHeadersForStream(Http2StreamId stream_id) {
   events_.push_back(absl::StrFormat("OnBeginHeadersForStream %d", stream_id));
+  return true;
 }
 
 Http2VisitorInterface::OnHeaderResult RecordingHttp2Visitor::OnHeaderForStream(
diff --git a/http2/adapter/recording_http2_visitor.h b/http2/adapter/recording_http2_visitor.h
index 501a476..25b9293 100644
--- a/http2/adapter/recording_http2_visitor.h
+++ b/http2/adapter/recording_http2_visitor.h
@@ -29,7 +29,7 @@
   void OnSetting(Http2Setting setting) override;
   void OnSettingsEnd() override;
   void OnSettingsAck() override;
-  void OnBeginHeadersForStream(Http2StreamId stream_id) override;
+  bool OnBeginHeadersForStream(Http2StreamId stream_id) override;
   OnHeaderResult OnHeaderForStream(Http2StreamId stream_id,
                                    absl::string_view name,
                                    absl::string_view value) override;