diff --git a/quic/api/QuicTransportBase.cpp b/quic/api/QuicTransportBase.cpp
index b5e9bab25..387b05ba4 100644
--- a/quic/api/QuicTransportBase.cpp
+++ b/quic/api/QuicTransportBase.cpp
@@ -390,8 +390,11 @@ void QuicTransportBase::closeImpl(
     if (noError) {
       connCallback_->onConnectionEnd();
     } else {
+      std::string closeStr = exceptionCloseWhat_
+          ? std::move(exceptionCloseWhat_.value())
+          : cancelCode.second.str();
       connCallback_->onConnectionError(
-          std::make_pair(cancelCode.first, cancelCode.second.str()));
+          std::make_pair(cancelCode.first, closeStr));
     }
   }
 
@@ -1279,16 +1282,19 @@ folly::Expected<std::pair<Buf, bool>, LocalErrorCode> QuicTransportBase::read(
     return folly::makeExpected<LocalErrorCode>(std::move(result));
   } catch (const QuicTransportException& ex) {
     VLOG(4) << "read() error " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("read() error")));
     return folly::makeUnexpected(LocalErrorCode::TRANSPORT_ERROR);
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("read() error")));
     return folly::makeUnexpected(ex.errorCode());
   } catch (const std::exception& ex) {
     VLOG(4) << "read()  error " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("read() error")));
@@ -1405,17 +1411,20 @@ folly::
     return folly::makeExpected<ConsumeError>(folly::Unit());
   } catch (const QuicTransportException& ex) {
     VLOG(4) << "consume() error " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("consume() error")));
     return folly::makeUnexpected(
         ConsumeError{LocalErrorCode::TRANSPORT_ERROR, readOffset});
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("consume() error")));
     return folly::makeUnexpected(ConsumeError{ex.errorCode(), readOffset});
   } catch (const std::exception& ex) {
     VLOG(4) << "consume() error " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("consume() error")));
@@ -1635,18 +1644,22 @@ void QuicTransportBase::onNetworkData(
     }
   } catch (const QuicTransportException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     return closeImpl(
         std::make_pair(QuicErrorCode(ex.errorCode()), std::string(ex.what())));
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     return closeImpl(
         std::make_pair(QuicErrorCode(ex.errorCode()), std::string(ex.what())));
   } catch (const QuicApplicationException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     return closeImpl(
         std::make_pair(QuicErrorCode(ex.errorCode()), std::string(ex.what())));
   } catch (const std::exception& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     return closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("error onNetworkData()")));
@@ -1868,18 +1881,21 @@ QuicSocket::WriteResult QuicTransportBase::writeChain(
   } catch (const QuicTransportException& ex) {
     VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
             << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("writeChain() error")));
     return folly::makeUnexpected(LocalErrorCode::TRANSPORT_ERROR);
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
             << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("writeChain() error")));
     return folly::makeUnexpected(ex.errorCode());
   } catch (const std::exception& ex) {
     VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
             << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("writeChain() error")));
@@ -1994,18 +2010,21 @@ folly::Expected<folly::Unit, LocalErrorCode> QuicTransportBase::resetStream(
   } catch (const QuicTransportException& ex) {
     VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
             << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("resetStream() error")));
     return folly::makeUnexpected(LocalErrorCode::TRANSPORT_ERROR);
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
             << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()), std::string("resetStream() error")));
     return folly::makeUnexpected(ex.errorCode());
   } catch (const std::exception& ex) {
     VLOG(4) << __func__ << " streamId=" << id << " " << ex.what() << " "
             << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("resetStream() error")));
@@ -2103,16 +2122,19 @@ void QuicTransportBase::lossTimeoutExpired() noexcept {
     pacedWriteDataToSocket(false);
   } catch (const QuicTransportException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()),
         std::string("lossTimeoutExpired() error")));
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << " " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()),
         std::string("lossTimeoutExpired() error")));
   } catch (const std::exception& ex) {
     VLOG(4) << __func__ << "  " << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("lossTimeoutExpired() error")));
@@ -2376,16 +2398,19 @@ void QuicTransportBase::writeSocketDataAndCatch() {
     writeSocketData();
   } catch (const QuicTransportException& ex) {
     VLOG(4) << __func__ << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()),
         std::string("writeSocketDataAndCatch()  error")));
   } catch (const QuicInternalException& ex) {
     VLOG(4) << __func__ << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(ex.errorCode()),
         std::string("writeSocketDataAndCatch()  error")));
   } catch (const std::exception& ex) {
     VLOG(4) << __func__ << " error=" << ex.what() << " " << *this;
+    exceptionCloseWhat_ = ex.what();
     closeImpl(std::make_pair(
         QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
         std::string("writeSocketDataAndCatch()  error")));
diff --git a/quic/api/QuicTransportBase.h b/quic/api/QuicTransportBase.h
index 1b355b542..37c211d62 100644
--- a/quic/api/QuicTransportBase.h
+++ b/quic/api/QuicTransportBase.h
@@ -627,6 +627,8 @@ class QuicTransportBase : public QuicSocket {
   folly::SocketAddress localFallbackAddress;
   // CongestionController factory
   std::shared_ptr<CongestionControllerFactory> ccFactory_{nullptr};
+
+  folly::Optional<std::string> exceptionCloseWhat_;
 };
 
 std::ostream& operator<<(std::ostream& os, const QuicTransportBase& qt);
diff --git a/quic/api/test/QuicTransportBaseTest.cpp b/quic/api/test/QuicTransportBaseTest.cpp
index 914ef9c7f..c74c3fd75 100644
--- a/quic/api/test/QuicTransportBaseTest.cpp
+++ b/quic/api/test/QuicTransportBaseTest.cpp
@@ -1030,6 +1030,30 @@ TEST_F(QuicTransportImplTest, ConnectionErrorOnWrite) {
       QuicErrorCode(LocalErrorCode::CONNECTION_ABANDONED));
 }
 
+TEST_F(QuicTransportImplTest, ConnectionErrorUnhandledException) {
+  transport->transportConn->oneRttWriteCipher = test::createNoOpAead();
+  auto stream = transport->createBidirectionalStream().value();
+  EXPECT_CALL(
+      connCallback,
+      onConnectionError(std::make_pair(
+          QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
+          std::string("Well there's your problem"))));
+  EXPECT_CALL(*socketPtr, write(_, _)).WillOnce(Invoke([](auto&, auto&) {
+    throw std::runtime_error("Well there's your problem");
+    return 0;
+  }));
+  QuicSocket::WriteResult result = transport->writeChain(
+      stream, folly::IOBuf::copyBuffer("Hey"), true, false, nullptr);
+  transport->addDataToStream(
+      stream, StreamBuffer(folly::IOBuf::copyBuffer("Data"), 0));
+  evb->loopOnce();
+
+  EXPECT_TRUE(transport->isClosed());
+  EXPECT_EQ(
+      transport->getConnectionError(),
+      QuicErrorCode(TransportErrorCode::INTERNAL_ERROR));
+}
+
 TEST_F(QuicTransportImplTest, LossTimeoutNoLessThanTickInterval) {
   auto tickInterval = evb->timer().getTickInterval();
   transport->scheduleLossTimeout(tickInterval - 1ms);