diff --git a/http2/adapter/header_validator.cc b/http2/adapter/header_validator.cc
index d4c5ee4..4111652 100644
--- a/http2/adapter/header_validator.cc
+++ b/http2/adapter/header_validator.cc
@@ -162,11 +162,14 @@
     return false;
   }
 
-  // TODO(diannahu): Do the same for 1xx responses.
   if (status_ == "204" && value != "0") {
     // There should be no body in a "204 No Content" response.
     return false;
   }
+  if (!status_.empty() && status_[0] == '1' && value != "0") {
+    // There should also be no body in a 1xx response.
+    return false;
+  }
 
   size_t content_length = 0;
   const bool valid = absl::SimpleAtoi(value, &content_length);
diff --git a/http2/adapter/header_validator_test.cc b/http2/adapter/header_validator_test.cc
index addb35a..ba6d06a 100644
--- a/http2/adapter/header_validator_test.cc
+++ b/http2/adapter/header_validator_test.cc
@@ -307,6 +307,42 @@
             v.ValidateSingleHeader("content-length", "1"));
 }
 
+TEST(HeaderValidatorTest, Response100) {
+  HeaderValidator v;
+
+  v.StartHeaderBlock();
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader(":status", "100"));
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader("x-content", "is not present"));
+  EXPECT_TRUE(v.FinishHeaderBlock(HeaderType::RESPONSE));
+}
+
+TEST(HeaderValidatorTest, Response100WithContentLengthZero) {
+  HeaderValidator v;
+
+  v.StartHeaderBlock();
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader(":status", "100"));
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader("x-content", "is not present"));
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader("content-length", "0"));
+  EXPECT_TRUE(v.FinishHeaderBlock(HeaderType::RESPONSE));
+}
+
+TEST(HeaderValidatorTest, Response100WithContentLength) {
+  HeaderValidator v;
+
+  v.StartHeaderBlock();
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader(":status", "100"));
+  EXPECT_EQ(HeaderValidator::HEADER_OK,
+            v.ValidateSingleHeader("x-content", "is not present"));
+  EXPECT_EQ(HeaderValidator::HEADER_FIELD_INVALID,
+            v.ValidateSingleHeader("content-length", "1"));
+}
+
 TEST(HeaderValidatorTest, ResponseTrailerPseudoHeaders) {
   HeaderValidator v;
 
diff --git a/http2/adapter/nghttp2_adapter_test.cc b/http2/adapter/nghttp2_adapter_test.cc
index c68dad5..b16241b 100644
--- a/http2/adapter/nghttp2_adapter_test.cc
+++ b/http2/adapter/nghttp2_adapter_test.cc
@@ -386,6 +386,75 @@
                                             spdy::SpdyFrameType::RST_STREAM}));
 }
 
+TEST(NgHttp2AdapterTest, ClientRejects100HeadersWithContentLength) {
+  DataSavingVisitor visitor;
+  auto adapter = NgHttp2Adapter::CreateClientAdapter(visitor);
+
+  testing::InSequence s;
+
+  const std::vector<Header> headers1 =
+      ToHeaders({{":method", "GET"},
+                 {":scheme", "http"},
+                 {":authority", "example.com"},
+                 {":path", "/this/is/request/one"}});
+
+  const int32_t stream_id1 = adapter->SubmitRequest(headers1, nullptr, nullptr);
+  ASSERT_GT(stream_id1, 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);
+  visitor.Clear();
+
+  const std::string stream_frames =
+      TestFrameSequence()
+          .ServerPreface()
+          .Headers(1, {{":status", "100"}, {"content-length", "42"}},
+                   /*fin=*/false)
+          .Headers(1,
+                   {{":status", "200"},
+                    {"server", "my-fake-server"},
+                    {"date", "Tue, 6 Apr 2021 12:54:01 GMT"}},
+                   /*fin=*/true)
+          .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));
+  EXPECT_CALL(visitor, OnHeaderForStream(1, ":status", "100"));
+  EXPECT_CALL(
+      visitor,
+      OnErrorDebug("Invalid HTTP header field was received: frame type: 1, "
+                   "stream: 1, name: [content-length], value: [42]"));
+  EXPECT_CALL(
+      visitor,
+      OnInvalidFrame(1, Http2VisitorInterface::InvalidFrameError::kHttpHeader));
+  EXPECT_CALL(visitor, OnFrameHeader(1, _, HEADERS, 5));
+
+  const int64_t stream_result = adapter->ProcessBytes(stream_frames);
+  EXPECT_EQ(stream_frames.size(), static_cast<size_t>(stream_result));
+
+  EXPECT_CALL(visitor, OnBeforeFrameSent(SETTINGS, 0, _, 0x1));
+  EXPECT_CALL(visitor, OnFrameSent(SETTINGS, 0, _, 0x1, 0));
+  EXPECT_CALL(visitor, OnBeforeFrameSent(RST_STREAM, 1, _, 0x0));
+  EXPECT_CALL(visitor,
+              OnFrameSent(RST_STREAM, 1, _, 0x0,
+                          static_cast<int>(Http2ErrorCode::PROTOCOL_ERROR)));
+  EXPECT_CALL(visitor, OnCloseStream(1, Http2ErrorCode::PROTOCOL_ERROR));
+
+  EXPECT_TRUE(adapter->want_write());
+  result = adapter->Send();
+  EXPECT_EQ(0, result);
+  EXPECT_THAT(visitor.data(), EqualsFrames({spdy::SpdyFrameType::SETTINGS,
+                                            spdy::SpdyFrameType::RST_STREAM}));
+}
+
 TEST(NgHttp2AdapterTest, ClientHandles204WithContent) {
   DataSavingVisitor visitor;
   auto adapter = NgHttp2Adapter::CreateClientAdapter(visitor);
diff --git a/http2/adapter/oghttp2_adapter_test.cc b/http2/adapter/oghttp2_adapter_test.cc
index 910fbc5..2d0adb7 100644
--- a/http2/adapter/oghttp2_adapter_test.cc
+++ b/http2/adapter/oghttp2_adapter_test.cc
@@ -469,6 +469,73 @@
                                             spdy::SpdyFrameType::RST_STREAM}));
 }
 
+TEST(OgHttp2AdapterClientTest, ClientRejects100HeadersWithContentLength) {
+  DataSavingVisitor visitor;
+  OgHttp2Adapter::Options options{.perspective = Perspective::kClient};
+  auto adapter = OgHttp2Adapter::Create(visitor, options);
+
+  testing::InSequence s;
+
+  const std::vector<Header> headers1 =
+      ToHeaders({{":method", "GET"},
+                 {":scheme", "http"},
+                 {":authority", "example.com"},
+                 {":path", "/this/is/request/one"}});
+
+  const int32_t stream_id1 = adapter->SubmitRequest(headers1, nullptr, nullptr);
+  ASSERT_GT(stream_id1, 0);
+
+  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);
+  visitor.Clear();
+
+  const std::string stream_frames =
+      TestFrameSequence()
+          .ServerPreface()
+          .Headers(1, {{":status", "100"}, {"content-length", "42"}},
+                   /*fin=*/false)
+          .Headers(1,
+                   {{":status", "200"},
+                    {"server", "my-fake-server"},
+                    {"date", "Tue, 6 Apr 2021 12:54:01 GMT"}},
+                   /*fin=*/true)
+          .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));
+  EXPECT_CALL(visitor, OnHeaderForStream(1, ":status", "100"));
+  EXPECT_CALL(
+      visitor,
+      OnInvalidFrame(1, Http2VisitorInterface::InvalidFrameError::kHttpHeader));
+
+  const int64_t stream_result = adapter->ProcessBytes(stream_frames);
+  EXPECT_EQ(stream_frames.size(), static_cast<size_t>(stream_result));
+
+  EXPECT_CALL(visitor, OnBeforeFrameSent(SETTINGS, 0, _, 0x1));
+  EXPECT_CALL(visitor, OnFrameSent(SETTINGS, 0, _, 0x1, 0));
+  EXPECT_CALL(visitor, OnBeforeFrameSent(RST_STREAM, 1, _, 0x0));
+  EXPECT_CALL(visitor,
+              OnFrameSent(RST_STREAM, 1, _, 0x0,
+                          static_cast<int>(Http2ErrorCode::PROTOCOL_ERROR)));
+  EXPECT_CALL(visitor, OnCloseStream(1, Http2ErrorCode::HTTP2_NO_ERROR));
+
+  EXPECT_TRUE(adapter->want_write());
+  result = adapter->Send();
+  EXPECT_EQ(0, result);
+  EXPECT_THAT(visitor.data(), EqualsFrames({spdy::SpdyFrameType::SETTINGS,
+                                            spdy::SpdyFrameType::RST_STREAM}));
+}
+
 TEST(OgHttp2AdapterClientTest, ClientHandles204WithContent) {
   DataSavingVisitor visitor;
   OgHttp2Adapter::Options options{.perspective = Perspective::kClient};
diff --git a/http2/adapter/oghttp2_session.cc b/http2/adapter/oghttp2_session.cc
index 256e23d..2467009 100644
--- a/http2/adapter/oghttp2_session.cc
+++ b/http2/adapter/oghttp2_session.cc
@@ -1119,7 +1119,7 @@
 spdy::SpdyHeadersHandlerInterface* OgHttp2Session::OnHeaderFrameStart(
     spdy::SpdyStreamId stream_id) {
   auto it = stream_map_.find(stream_id);
-  if (it != stream_map_.end()) {
+  if (it != stream_map_.end() && !streams_reset_.contains(stream_id)) {
     headers_handler_.set_stream_id(stream_id);
     headers_handler_.set_header_type(
         NextHeaderType(it->second.received_header_type));