diff --git a/src/net/quic/quic_proxy_client_socket.cc b/src/net/quic/quic_proxy_client_socket.cc
index 2d04bdf441..3d8b0c6a34 100644
--- a/src/net/quic/quic_proxy_client_socket.cc
+++ b/src/net/quic/quic_proxy_client_socket.cc
@@ -38,6 +38,10 @@ QuicProxyClientSocket::QuicProxyClientSocket(
       auth_(auth_controller),
       user_agent_(user_agent),
       redirect_has_load_timing_info_(false),
+      // This is a hack to avoid messing up higer APIs.
+      // Should be false by default officially.
+      use_fastopen_(true),
+      read_headers_pending_(false),
       net_log_(net_log),
       weak_factory_(this) {
   DCHECK(stream_->IsOpen());
@@ -309,6 +313,20 @@ int QuicProxyClientSocket::DoLoop(int last_io_result) {
         rv = DoReadReplyComplete(rv);
         net_log_.EndEventWithNetErrorCode(
             NetLogEventType::HTTP_TRANSACTION_TUNNEL_READ_HEADERS, rv);
+        if (use_fastopen_ && read_headers_pending_) {
+          read_headers_pending_ = false;
+          if (rv < 0) {
+            // read_callback_ cannot be called.
+            if (!read_callback_)
+              rv = ERR_IO_PENDING;
+            // read_callback_ will be called with this error and be reset.
+            // Further data after that will be ignored.
+            next_state_ = STATE_DISCONNECTED;
+          } else {
+            // Does not call read_callback_ from here if headers are OK.
+            rv = ERR_IO_PENDING;
+          }
+        }
         break;
       default:
         NOTREACHED() << "bad state";
@@ -382,6 +400,11 @@ int QuicProxyClientSocket::DoReadReply() {
       &response_header_block_,
       base::Bind(&QuicProxyClientSocket::OnReadResponseHeadersComplete,
                  weak_factory_.GetWeakPtr()));
+  if (use_fastopen_ && rv == ERR_IO_PENDING) {
+    read_headers_pending_ = true;
+    next_state_ = STATE_CONNECT_COMPLETE;
+    return OK;
+  }
   if (rv == ERR_IO_PENDING)
     return ERR_IO_PENDING;
   if (rv < 0)
@@ -431,6 +454,11 @@ int QuicProxyClientSocket::DoReadReplyComplete(int result) {
 }
 
 void QuicProxyClientSocket::OnReadResponseHeadersComplete(int result) {
+  if (use_fastopen_ && read_headers_pending_ &&
+      next_state_ == STATE_CONNECT_COMPLETE) {
+    next_state_ = STATE_READ_REPLY_COMPLETE;
+  }
+
   // Convert the now-populated spdy::SpdyHeaderBlock to HttpResponseInfo
   if (result > 0)
     result = ProcessResponseHeaders(response_header_block_);
diff --git a/src/net/quic/quic_proxy_client_socket.h b/src/net/quic/quic_proxy_client_socket.h
index b9688eced3..5ccaf04131 100644
--- a/src/net/quic/quic_proxy_client_socket.h
+++ b/src/net/quic/quic_proxy_client_socket.h
@@ -147,6 +147,9 @@ class NET_EXPORT_PRIVATE QuicProxyClientSocket : public ProxyClientSocket {
   // Session connect timing info.
   LoadTimingInfo::ConnectTiming connect_timing_;
 
+  bool use_fastopen_;
+  bool read_headers_pending_;
+
   const NetLogWithSource net_log_;
 
   // The default weak pointer factory.