diff --git a/doc/h2load.h2r b/doc/h2load.h2r
index ccefdd1d..10cc5d56 100644
--- a/doc/h2load.h2r
+++ b/doc/h2load.h2r
@@ -49,6 +49,15 @@ time for request
     The fraction of the number of requests within standard deviation
     range (mean +/- sd) against total number of successful requests.
 
+FLOW CONTROL
+------------
+
+h2load sets large flow control window by default, and effectively
+disables flow control to avoid under utilization of server
+performance.  To set smaller flow control window, use :option:`-w` and
+:option:`-W` options.  For example, use ``-w16 -W16`` to set default
+window size described in HTTP/2 and SPDY protocol specification.
+
 SEE ALSO
 --------
 
diff --git a/src/h2load.cc b/src/h2load.cc
index 5daff7b0..37517d3e 100644
--- a/src/h2load.cc
+++ b/src/h2load.cc
@@ -69,7 +69,7 @@ namespace h2load {
 
 Config::Config()
     : data_length(-1), addrs(nullptr), nreqs(1), nclients(1), nthreads(1),
-      max_concurrent_streams(-1), window_bits(16), connection_window_bits(16),
+      max_concurrent_streams(-1), window_bits(30), connection_window_bits(30),
       no_tls_proto(PROTO_HTTP2), data_fd(-1), port(0), default_port(0),
       verbose(false) {}
 
@@ -974,11 +974,13 @@ Options:
   -w, --window-bits=<N>
               Sets the stream level initial window size to (2**<N>)-1.
               For SPDY, 2**<N> is used instead.
+              Default: )" << config.window_bits << R"(
   -W, --connection-window-bits=<N>
               Sets  the  connection  level   initial  window  size  to
               (2**<N>)-1.  For SPDY, if <N>  is strictly less than 16,
               this option  is ignored.   Otherwise 2**<N> is  used for
               SPDY.
+              Default: )" << config.connection_window_bits << R"(
   -H, --header=<HEADER>
               Add/Override a header to the requests.
   -p, --no-tls-proto=<PROTOID>