diff --git a/http2/adapter/http2_visitor_interface.h b/http2/adapter/http2_visitor_interface.h
index 308f0d8..8297334 100644
--- a/http2/adapter/http2_visitor_interface.h
+++ b/http2/adapter/http2_visitor_interface.h
@@ -52,8 +52,8 @@
   Http2VisitorInterface& operator=(const Http2VisitorInterface&) = delete;
   virtual ~Http2VisitorInterface() = default;
 
-  static const int64_t kSendBlocked = 0;
-  static const int64_t kSendError = -1;
+  static constexpr int64_t kSendBlocked = 0;
+  static constexpr int64_t kSendError = -1;
   // Called when there are serialized frames to send. Should return how many
   // bytes were actually sent. May return kSendBlocked or kSendError.
   virtual int64_t OnReadyToSend(absl::string_view serialized) = 0;
diff --git a/http2/adapter/nghttp2_adapter_test.cc b/http2/adapter/nghttp2_adapter_test.cc
index a61c55c..ccfb1ac 100644
--- a/http2/adapter/nghttp2_adapter_test.cc
+++ b/http2/adapter/nghttp2_adapter_test.cc
@@ -1386,6 +1386,17 @@
   EXPECT_FALSE(adapter->want_write());
 }
 
+TEST(NgHttp2AdapterTest, FailureSendingConnectionPreface) {
+  DataSavingVisitor visitor;
+  auto adapter = NgHttp2Adapter::CreateClientAdapter(visitor);
+
+  visitor.set_has_write_error();
+  EXPECT_CALL(visitor, OnConnectionError);
+
+  int result = adapter->Send();
+  EXPECT_EQ(result, NGHTTP2_ERR_CALLBACK_FAILURE);
+}
+
 TEST(NgHttp2AdapterTest, ServerConstruction) {
   testing::StrictMock<MockHttp2Visitor> visitor;
   auto adapter = NgHttp2Adapter::CreateServerAdapter(visitor);
diff --git a/http2/adapter/oghttp2_adapter_test.cc b/http2/adapter/oghttp2_adapter_test.cc
index 0efb679..f663fb7 100644
--- a/http2/adapter/oghttp2_adapter_test.cc
+++ b/http2/adapter/oghttp2_adapter_test.cc
@@ -4,6 +4,7 @@
 
 #include "absl/strings/str_join.h"
 #include "http2/adapter/http2_protocol.h"
+#include "http2/adapter/http2_visitor_interface.h"
 #include "http2/adapter/mock_http2_visitor.h"
 #include "http2/adapter/oghttp2_util.h"
 #include "http2/adapter/test_frame_sequence.h"
@@ -822,6 +823,18 @@
   EXPECT_FALSE(adapter->want_write());
 }
 
+TEST(OgHttp2AdapterClientTest, FailureSendingConnectionPreface) {
+  DataSavingVisitor visitor;
+  OgHttp2Adapter::Options options{.perspective = Perspective::kClient};
+  auto adapter = OgHttp2Adapter::Create(visitor, options);
+
+  visitor.set_has_write_error();
+  EXPECT_CALL(visitor, OnConnectionError);
+
+  int result = adapter->Send();
+  EXPECT_EQ(result, Http2VisitorInterface::kSendError);
+}
+
 TEST_F(OgHttp2AdapterTest, SubmitMetadata) {
   auto source = absl::make_unique<TestMetadataSource>(ToHeaderBlock(ToHeaders(
       {{"query-cost", "is too darn high"}, {"secret-sauce", "hollandaise"}})));
diff --git a/http2/adapter/oghttp2_session.cc b/http2/adapter/oghttp2_session.cc
index 4359bbf..149a026 100644
--- a/http2/adapter/oghttp2_session.cc
+++ b/http2/adapter/oghttp2_session.cc
@@ -299,9 +299,13 @@
       serialized_prefix_.erase(0, result);
     }
   }
-  if (!serialized_prefix_.empty()) {
-    return result < 0 ? result : 0;
+  if (result < 0) {
+    visitor_.OnConnectionError();
+    return result;
+  } else if (!serialized_prefix_.empty()) {
+    return 0;
   }
+
   bool continue_writing = SendQueuedFrames();
   while (continue_writing && !connection_metadata_.empty()) {
     continue_writing = SendMetadata(0, connection_metadata_);
diff --git a/http2/adapter/test_utils.h b/http2/adapter/test_utils.h
index 0493788..ec7e95c 100644
--- a/http2/adapter/test_utils.h
+++ b/http2/adapter/test_utils.h
@@ -23,6 +23,9 @@
     : public testing::StrictMock<MockHttp2Visitor> {
  public:
   int64_t OnReadyToSend(absl::string_view data) override {
+    if (has_write_error_) {
+      return kSendError;
+    }
     if (is_write_blocked_) {
       return kSendBlocked;
     }
@@ -63,11 +66,14 @@
   bool is_write_blocked() const { return is_write_blocked_; }
   void set_is_write_blocked(bool value) { is_write_blocked_ = value; }
 
+  void set_has_write_error() { has_write_error_ = true; }
+
  private:
   std::string data_;
   absl::flat_hash_map<Http2StreamId, std::vector<std::string>> metadata_map_;
   size_t send_limit_ = std::numeric_limits<size_t>::max();
   bool is_write_blocked_ = false;
+  bool has_write_error_ = false;
 };
 
 // A test DataFrameSource. Starts out in the empty, blocked state.