new file mode 100644
--- /dev/null
+++ b/addition_buffered.t
@@ -0,0 +1,72 @@
+#!/usr/bin/perl
+
+# (C) Sergey Kandaurov
+# (C) Nginx, Inc.
+
+# Tests for addition module with buffered data from other filters.
+
+# In particular, sub filter may have a partial match buffered.
+
+###############################################################################
+
+use warnings;
+use strict;
+
+use Test::More;
+
+BEGIN { use FindBin; chdir($FindBin::Bin); }
+
+use lib 'lib';
+use Test::Nginx;
+
+###############################################################################
+
+select STDERR; $| = 1;
+select STDOUT; $| = 1;
+
+my $t = Test::Nginx->new()->has(qw/http proxy sub addition/)->plan(1);
+
+$t->write_file_expand('nginx.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / { }
+        location /proxy/ {
+            sub_filter foo bar;
+            add_after_body /after.html;
+            proxy_pass http://127.0.0.1:8080/;
+        }
+    }
+}
+
+EOF
+
+$t->write_file('after.html', 'after');
+$t->write_file('body.html', 'XXXXX');
+
+$t->run();
+
+###############################################################################
+
+# if data is buffered, there should be no interleaved data in output 
+
+TODO: {
+local $TODO = 'not yet' unless $t->has_version('1.11.5');
+
+like(http_get('/proxy/body.html'), qr/^XXXXXafter$/m, 'request');
+
+}
+
+###############################################################################