diff --git a/net/spdy/chromium/spdy_proxy_client_socket.cc b/net/spdy/chromium/spdy_proxy_client_socket.cc
index fb1168aa05..312e5f5364 100644
--- a/net/spdy/chromium/spdy_proxy_client_socket.cc
+++ b/net/spdy/chromium/spdy_proxy_client_socket.cc
@@ -45,6 +45,10 @@ SpdyProxyClientSocket::SpdyProxyClientSocket(
       write_buffer_len_(0),
       was_ever_used_(false),
       redirect_has_load_timing_info_(false),
+      // This is a hack to avoid messing up higher APIs.
+      // Should be false by default officially.
+      use_fastopen_(true),
+      read_headers_pending_(false),
       net_log_(NetLogWithSource::Make(spdy_stream->net_log().net_log(),
                                       NetLogSourceType::PROXY_CLIENT_SOCKET)),
       source_dependency_(source_net_log.source()),
@@ -314,6 +318,20 @@ int SpdyProxyClientSocket::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";
@@ -371,6 +389,12 @@ int SpdyProxyClientSocket::DoSendRequestComplete(int result) {
   if (result < 0)
     return result;
 
+  if (use_fastopen_) {
+    read_headers_pending_ = true;
+    next_state_ = STATE_OPEN;
+    return OK;
+  }
+
   // Wait for HEADERS frame from the server
   next_state_ = STATE_READ_REPLY_COMPLETE;
   return ERR_IO_PENDING;
@@ -438,6 +462,10 @@ void SpdyProxyClientSocket::OnHeadersSent() {
 
 void SpdyProxyClientSocket::OnHeadersReceived(
     const SpdyHeaderBlock& response_headers) {
+  if (use_fastopen_ && read_headers_pending_ && next_state_ == STATE_OPEN) {
+    next_state_ = STATE_READ_REPLY_COMPLETE;
+  }
+
   // If we've already received the reply, existing headers are too late.
   // TODO(mbelshe): figure out a way to make HEADERS frames useful after the
   //                initial response.
diff --git a/net/spdy/chromium/spdy_proxy_client_socket.h b/net/spdy/chromium/spdy_proxy_client_socket.h
index 60c095a996..e8324518a4 100644
--- a/net/spdy/chromium/spdy_proxy_client_socket.h
+++ b/net/spdy/chromium/spdy_proxy_client_socket.h
@@ -170,6 +170,9 @@ class NET_EXPORT_PRIVATE SpdyProxyClientSocket : public ProxyClientSocket,
   bool redirect_has_load_timing_info_;
   LoadTimingInfo redirect_load_timing_info_;
 
+  bool use_fastopen_;
+  bool read_headers_pending_;
+
   const NetLogWithSource net_log_;
   const NetLogSource source_dependency_;