new file mode 100644
--- /dev/null
+++ b/proxy_cache_lock_ssi.t
@@ -0,0 +1,110 @@
+#!/usr/bin/perl
+
+# (C) Maxim Dounin
+
+# Tests for http proxy cache lock with subrequests.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx qw/ :DEFAULT http_end /;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+plan(skip_all => 'win32') if $^O eq 'MSWin32';
+
+my $t = Test::Nginx->new()->has(qw/http proxy cache ssi/)
+	->write_file_expand('nginx.conf', <<'EOF')->plan(2);
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    proxy_cache_path   %%TESTDIR%%/cache  levels=1:2
+                       keys_zone=NAME:1m;
+
+    limit_req_zone $binary_remote_addr zone=one:1m rate=1r/m;
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / {
+            proxy_pass    http://127.0.0.1:8081;
+            proxy_cache   NAME;
+
+            proxy_cache_lock on;
+            proxy_cache_lock_timeout 100ms;
+
+            proxy_read_timeout 2s;
+        }
+
+        location = /ssi.html {
+            ssi on;
+        }
+    }
+
+    server {
+        listen       127.0.0.1:8081;
+        server_name  localhost;
+        limit_req zone=one burst=5;
+    }
+
+}
+
+EOF
+
+$t->write_file('ssi.html',
+	'<!--#include virtual="/active" -->' .
+	'<!--#include virtual="/locked" -->' .
+	'end'
+);
+
+$t->write_file('active', 'active');
+$t->write_file('locked', 'locked');
+
+$t->run();
+
+###############################################################################
+
+# problem: if proxy cache lock wakeup happens in a an inactive
+# subrequest, just a connection write event may not trigger any
+# further work
+
+# main request -> subrequest /active (waiting for a backend),
+#              -> subrequest /locked (locked by another request)
+
+# this doesn't result in an infinite timeout as second subrequest
+# is woken up by the postpone filter once first subrequest completes,
+# but this is suboptimal behaviour
+
+my $start = time();
+
+my $s = http_get('/locked', start => 1);
+like(http_get('/ssi.html'), qr/end/, 'cache lock ssi');
+http_end($s);
+
+TODO: {
+local $TODO = 'not yet';
+
+cmp_ok(time() - $start, '<=', 3, 'parallel execution after lock timeout');
+
+}
+
+###############################################################################