diff --git a/doc/configuration.txt b/doc/configuration.txt
index 9e28a282f..34e07f3cf 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -3478,12 +3478,12 @@ tune.h2.fe.initial-window-size <number>
   from HAProxy. This setting only affects payload contents (i.e. the body of
   POST requests), not headers. When not set, the common default value set by
   tune.h2.initial-window-size applies. It can make sense to increase this value
-  to allow faster uploads. The default value of 65536 allows at least 5 Mbps of
-  bandwidth per stream over a 100 ms ping time, and 500 Mbps for 1 ms ping
-  time. It doesn't affect resource usage. Using too large values may cause
-  clients to experience a lack of responsiveness if pages are accessed in
-  parallel to large uploads. It is better to use tune.h2.fe.rxbuf instead,
-  which does not cause any unfairness.
+  to allow faster uploads. The default value equals tune.bufsize (16384) and
+  allows at least 1.25 Mbps of bandwidth per stream over a 100 ms ping time,
+  and 125 Mbps for 1 ms ping time. It doesn't affect resource usage. Using too
+  large values may cause clients to experience a lack of responsiveness if
+  pages are accessed in parallel to large uploads. It is better to use
+  tune.h2.fe.rxbuf instead, which does not cause any unfairness.
 
   See also: tune.h2.initial-window-size.
 
@@ -3559,16 +3559,17 @@ tune.h2.initial-window-size <number>
   and outgoing connections. This value is used for incoming connections when
   tune.h2.fe.initial-window-size is not set, and by outgoing connections when
   tune.h2.be.initial-window-size is not set. This setting is used both as the
-  initial value and as a minimum per stream. The default value is 65536, which
-  for uploads roughly allows at least 5 Mbps of bandwidth per stream over a
-  network showing a 100 ms ping time, or 500 Mbps over a 1-ms local network.
-  When less receive buffers than the maximum are in use, within the limits
-  defined by tune.h2.be.rxbuf and tune.h2.fe.rxbuf, unused buffers will be
-  shared between receiving streams. As such there is normally no point in
-  changing this default setting. Given that changing this default value will
-  both increase upload speeds and cause more unfairness between clients on
-  downloads, it is recommended to instead use the side-specific settings
-  tune.h2.fe.initial-window-size and tune.h2.be.initial-window-size.
+  initial value and as a minimum per stream. The default value equals 16384
+  (tune.bufsize), which for uploads roughly allows at least 1.25 Mbps of
+  bandwidth per stream over a network showing a 100 ms ping time, or 125 Mbps
+  over a 1-ms local network. When less receive buffers than the maximum are in
+  use, within the limits defined by tune.h2.be.rxbuf and tune.h2.fe.rxbuf,
+  unused buffers will be shared between receiving streams. As such there is
+  normally no point in changing this default setting. Given that changing this
+  default value will both increase upload speeds and cause more unfairness
+  between clients on downloads, it is recommended to instead use the side-
+  specific settings tune.h2.fe.initial-window-size and
+  tune.h2.be.initial-window-size.
 
 tune.h2.max-concurrent-streams <number>
   Sets the default HTTP/2 maximum number of concurrent streams per connection
diff --git a/src/mux_h2.c b/src/mux_h2.c
index a5c03b50f..6063aed93 100644
--- a/src/mux_h2.c
+++ b/src/mux_h2.c
@@ -463,7 +463,7 @@ struct pool_head *pool_head_h2_rx_bufs __read_mostly = NULL;
 
 /* a few settings from the global section */
 static int h2_settings_header_table_size      =  4096; /* initial value */
-static int h2_settings_initial_window_size    = 65536; /* default initial value */
+static int h2_settings_initial_window_size    =     0; /* default initial value: bufsize */
 static int h2_be_settings_initial_window_size =     0; /* backend's default initial value */
 static int h2_fe_settings_initial_window_size =     0; /* frontend's default initial value */
 static int h2_be_glitches_threshold           =     0; /* backend's max glitches: unlimited */
@@ -8341,6 +8341,10 @@ static int init_h2()
 		return (ERR_ALERT | ERR_FATAL);
 	}
 
+	if (!h2_settings_initial_window_size)
+		h2_settings_initial_window_size =
+			MAX(16384, global.tune.bufsize - sizeof(struct htx) - sizeof(struct htx_blk));
+
 	max_bufs = h2_fe_settings_max_concurrent_streams ?
 	           h2_fe_settings_max_concurrent_streams :
 	           h2_settings_max_concurrent_streams;