diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 76cab5d3b62d078bf798d266190ce1a82a650205..710e9d239ecef9248bf0d8443687bc2d1b7523cd 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -228,6 +228,9 @@ tcp_allowed_congestion_control - STRING
 tcp_app_win - INTEGER
 	Reserve max(window/2^tcp_app_win, mss) of window for application
 	buffer. Value 0 is special, it means that nothing is reserved.
+
+	Possible values are [0, 31], inclusive.
+
 	Default: 31
 
 tcp_autocorking - BOOLEAN
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 5d18e956cbe16952cc3c3350cfaeed1068012cd7..2644e1249a42f905333e9abb2b75cf1f7f14349f 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -39,6 +39,7 @@ static int ip_local_port_range_min[] = { 1, 1 };
 static int ip_local_port_range_max[] = { 65535, 65535 };
 static int tcp_adv_win_scale_min = -31;
 static int tcp_adv_win_scale_max = 31;
+static int tcp_app_win_max = 31;
 static int tcp_min_snd_mss_min = TCP_MIN_SND_MSS;
 static int tcp_min_snd_mss_max = 65535;
 static int ip_privileged_port_min;
@@ -1084,7 +1085,9 @@ static struct ctl_table ipv4_net_table[] = {
 		.data		= &init_net.ipv4.sysctl_tcp_app_win,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &tcp_app_win_max,
 	},
 	{
 		.procname	= "tcp_adv_win_scale",