new file mode 100644
--- /dev/null
+++ b/not_modified_finalize.t
@@ -0,0 +1,91 @@
+#!/usr/bin/perl
+
+# (C) Maxim Dounin
+
+# Tests for not modified filter and filter finalization.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx qw/ :DEFAULT :gzip /;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+my $t = Test::Nginx->new()->has(qw/http proxy cache/)->plan(1)
+	->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    proxy_cache_path %%TESTDIR%%/cache keys_zone=cache:1m;
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        error_page 412 /error412.html;
+
+        location / {
+            proxy_pass        http://127.0.0.1:8081;
+            proxy_cache       cache;
+            proxy_cache_lock  on;
+        }
+
+        location /error412 {
+        }
+    }
+
+    server {
+        listen       127.0.0.1:8081;
+        server_name  localhost;
+    }
+}
+
+EOF
+
+$t->write_file('t.html', 'test file');
+$t->write_file('error412.html', 'error412');
+
+$t->run();
+
+###############################################################################
+
+# we trigger filter finalization in not modified filter by using
+# the If-Unmodified-Since/If-Match header;
+# with cache enabled and updating bit set, this currently results in
+# "stalled cache updating" alerts
+
+like(http_match_get('/t.html'), qr//, 'request 412');
+
+$t->todo_alerts();
+
+###############################################################################
+
+sub http_match_get {
+	my ($url, %extra) = @_;
+	return http(<<EOF, %extra);
+GET $url HTTP/1.0
+Host: localhost
+If-Match: tt
+
+EOF
+}
+
+###############################################################################