diff --git a/client_body_buffer_size.t b/client_body_buffer_size.t
new file mode 100644
index 00000000..47ca94d6
--- /dev/null
+++ b/client_body_buffer_size.t
@@ -0,0 +1,193 @@
+#!/usr/bin/perl
+
+# (C) Nginx, Inc.
+
+# Tests for client_body_buffer_size configuration validation.
+
+###############################################################################
+
+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/)->plan(10);
+
+my $d = $t->testdir;
+
+# Empty error.log so DESTROY-time "no alerts" / "no sanitizer errors"
+# checks have a file to read; nginx is invoked with -t only and never
+# starts as a daemon in this test.
+
+$t->write_file('error.log', '');
+
+###############################################################################
+
+# zero value rejected at location scope
+
+$t->write_file_expand('zero-location.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / {
+            client_body_buffer_size 0;
+        }
+    }
+}
+
+EOF
+
+my $out = `$Test::Nginx::NGINX -t -p $d/ -c zero-location.conf -e error.log 2>&1`;
+isnt($? >> 8, 0, 'zero value at location scope rejected');
+like($out, qr/\[emerg\].*client body buffer size cannot be zero/,
+	'emerg message at location scope');
+
+# zero value rejected at server scope
+
+$t->write_file_expand('zero-server.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        client_body_buffer_size 0;
+    }
+}
+
+EOF
+
+$out = `$Test::Nginx::NGINX -t -p $d/ -c zero-server.conf -e error.log 2>&1`;
+isnt($? >> 8, 0, 'zero value at server scope rejected');
+like($out, qr/\[emerg\].*client body buffer size cannot be zero/,
+	'emerg message at server scope');
+
+# zero value rejected at http scope
+
+$t->write_file_expand('zero-http.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    client_body_buffer_size 0;
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+    }
+}
+
+EOF
+
+$out = `$Test::Nginx::NGINX -t -p $d/ -c zero-http.conf -e error.log 2>&1`;
+isnt($? >> 8, 0, 'zero value at http scope rejected');
+like($out, qr/\[emerg\].*client body buffer size cannot be zero/,
+	'emerg message at http scope');
+
+# zero value with a size suffix also rejected ("0k" parses to 0)
+
+$t->write_file_expand('zero-suffix.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / {
+            client_body_buffer_size 0k;
+        }
+    }
+}
+
+EOF
+
+$out = `$Test::Nginx::NGINX -t -p $d/ -c zero-suffix.conf -e error.log 2>&1`;
+isnt($? >> 8, 0, 'zero value with size suffix rejected');
+like($out, qr/\[emerg\].*client body buffer size cannot be zero/,
+	'emerg message with size suffix');
+
+# valid values accepted
+
+$t->write_file_expand('valid.conf', <<'EOF');
+
+%%TEST_GLOBALS%%
+
+daemon off;
+
+events {
+}
+
+http {
+    %%TEST_GLOBALS_HTTP%%
+
+    server {
+        listen       127.0.0.1:8080;
+        server_name  localhost;
+
+        location / {
+            client_body_buffer_size 1;
+        }
+
+        location /default {
+        }
+
+        location /size {
+            client_body_buffer_size 8k;
+        }
+    }
+}
+
+EOF
+
+$out = `$Test::Nginx::NGINX -t -p $d/ -c valid.conf -e error.log 2>&1`;
+is($? >> 8, 0, 'valid values accepted');
+unlike($out, qr/\[emerg\]/, 'no emerg for valid values');
+
+###############################################################################