diff --git a/proxy_implicit.t b/proxy_implicit.t
new file mode 100644
index 0000000..e5b9cb4
--- /dev/null
+++ b/proxy_implicit.t
@@ -0,0 +1,105 @@
+#!/usr/bin/perl
+
+# (C) Sergey Kandaurov
+# (C) Nginx, Inc.
+
+# Tests for an upstream implicitly defined by proxy_pass.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+use Socket qw/ SOCK_STREAM IPPROTO_TCP AF_INET6 /;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+eval { die if $Socket::VERSION < 1.96; };
+plan(skip_all => 'Socket too old for getaddrinfo') if $@;
+
+my $t = Test::Nginx->new()->has(qw/http proxy/);
+
+$t->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        listen       [::1]:%%PORT_8080%%;
+        server_name  localhost;
+
+        location / {
+            proxy_pass http://localhost:%%PORT_8080%%/stub;
+            proxy_next_upstream http_404;
+            add_header X-Addr $upstream_addr always;
+        }
+
+        location /var {
+            proxy_pass http://$arg_b/stub;
+            proxy_next_upstream http_404;
+            add_header X-Addr $upstream_addr always;
+        }
+
+        location /stub { }
+    }
+}
+
+EOF
+
+$t->try_run('no inet6 support')->plan(3);
+
+###############################################################################
+
+my $p = port(8080);
+my @addrs = resolve('localhost');
+my $exp = qr/$addrs[0]:$p/ if @addrs == 1;
+my $v1 = "$addrs[0]:$p", my $v2 = "$addrs[1]:$p" if @addrs == 2;
+$exp = qr/\Q$v1, $v2\E|\Q$v2, $v1\E/ if @addrs == 2;
+die "too many addresses in localhost" if @addrs > 2;
+
+like(http_get('/'), qr/Not Found/, 'implicit upstream');
+like(http_get('/'), $exp, 'implicit upstream all tried');
+like(http_get("/var?b=localhost:$p"), qr/Not Found/,
+	'implicit upstream by variable');
+
+###############################################################################
+
+sub resolve {
+	my ($name) = @_;
+
+	my $ai_addrconfig = eval { Socket::AI_ADDRCONFIG() };
+	my ($err, @res) = Socket::getaddrinfo($name, "",
+		{ socktype => SOCK_STREAM, protocol => IPPROTO_TCP,
+			flags => $ai_addrconfig });
+	die "Cannot getaddrinfo - $err" if $err;
+
+	my @addrs;
+	foreach my $ai (@res) {
+		my ($err, $addr) = Socket::getnameinfo($ai->{addr},
+			Socket::NI_NUMERICHOST(), Socket::NIx_NOSERV());
+		die "Cannot getnameinfo - $err" if $err;
+		$addr = '[' . $addr . ']' if $ai->{family} == AF_INET6;
+		push @addrs, $addr;
+	}
+	return @addrs;
+}
+
+###############################################################################