diff --git a/src/net/spdy/spdy_proxy_client_socket.cc b/src/net/spdy/spdy_proxy_client_socket.cc
index 831ae1cbb7..d676ef1786 100644
--- a/src/net/spdy/spdy_proxy_client_socket.cc
+++ b/src/net/spdy/spdy_proxy_client_socket.cc
@@ -334,6 +334,20 @@ 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_IN_MIGRATION() << "bad state";
@@ -377,6 +391,10 @@ int SpdyProxyClientSocket::DoSendRequest() {
     if (result < 0) {
       return result;
     }
+    if (proxy_delegate_headers.HasHeader("fastopen")) {
+      proxy_delegate_headers.RemoveHeader("fastopen");
+      use_fastopen_ = true;
+    }
     request_.extra_headers.MergeFrom(proxy_delegate_headers);
   }
 
@@ -400,6 +418,12 @@ 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;
@@ -460,6 +484,10 @@ void SpdyProxyClientSocket::OnEarlyHintsReceived(
 
 void SpdyProxyClientSocket::OnHeadersReceived(
     const quiche::HttpHeaderBlock& 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/src/net/spdy/spdy_proxy_client_socket.h b/src/net/spdy/spdy_proxy_client_socket.h
index 7b8b20bcd5..74953b3bdf 100644
--- a/src/net/spdy/spdy_proxy_client_socket.h
+++ b/src/net/spdy/spdy_proxy_client_socket.h
@@ -182,6 +182,9 @@ class NET_EXPORT_PRIVATE SpdyProxyClientSocket : public ProxyClientSocket,
   // True if the transport socket has ever sent data.
   bool was_ever_used_ = false;
 
+  bool use_fastopen_ = false;
+  bool read_headers_pending_ = false;
+
   const NetLogWithSource net_log_;
   const NetLogSource source_dependency_;