diff --git a/t/pt-online-schema-change/rename_fk_constraints.t b/t/pt-online-schema-change/rename_fk_constraints.t
index 1c8b13f5..f064ccfe 100644
--- a/t/pt-online-schema-change/rename_fk_constraints.t
+++ b/t/pt-online-schema-change/rename_fk_constraints.t
@@ -42,7 +42,7 @@ my $sample  = "t/pt-online-schema-change/samples/";
 $sb->load_file('master', "$sample/bug-1215587.sql");
 
 # run once: we expect constraint names to be prefixed with one underscore
-# if they havre't one, and to remove one if they already do.
+# if they havre't one, and to remove 2 if they have 2
 ($output, $exit_status) = full_output(
    sub { pt_online_schema_change::main(@args,
       "$master_dsn,D=bug1215587,t=Table1",
@@ -50,25 +50,46 @@ $sb->load_file('master', "$sample/bug-1215587.sql");
       qw(--execute)) },
 );
 
-
 my $constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1215587' and (TABLE_NAME='Table1' OR TABLE_NAME='Table2') and CONSTRAINT_NAME LIKE '%fkey%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
 
 
 is_deeply(
    $constraints,
    [
-      ['Table1', 'fkey1a'],
       ['Table1', '_fkey1b'],
-      ['Table2', 'fkey2b'],
+      ['Table1', '__fkey1a'],
       ['Table2', '_fkey2a'],
+      ['Table2', '__fkey2b'],
    ],
    "First run adds or removes underscore from constraint names, accordingly"
 );
 
 
 
-# run second time 
-# we expect constraints to be the same as we started (toggled back)
+# run second time: we expect constraint names to be prefixed with one underscore
+# if they havre't one, and to remove 2 if they have 2
+($output, $exit_status) = full_output(
+   sub { pt_online_schema_change::main(@args,
+      "$master_dsn,D=bug1215587,t=Table1",
+      "--alter", "ENGINE=InnoDB",
+      qw(--execute)) },
+);
+
+$constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1215587' and (TABLE_NAME='Table1' OR TABLE_NAME='Table2') and CONSTRAINT_NAME LIKE '%fkey%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
+
+
+is_deeply(
+   $constraints,
+   [
+      ['Table1', 'fkey1a'],
+      ['Table1', '__fkey1b'],
+      ['Table2', 'fkey2b'],
+      ['Table2', '__fkey2a'],
+   ],
+   "Second run adds or removes underscore from constraint names, accordingly"
+);
+
+# run third time: we expect constraints to be the same as we started (toggled back)
 ($output, $exit_status) = full_output(
    sub { pt_online_schema_change::main(@args,
       "$master_dsn,D=bug1215587,t=Table1",
@@ -87,10 +108,9 @@ is_deeply(
       ['Table2', 'fkey2a'],
       ['Table2', '_fkey2b'],
    ],
-   "Second run toggles constraint names back to how they were"
+   "Third run toggles constraint names back to how they were"
 );
 
-
 # #############################################################################
 # Done.
 # #############################################################################
diff --git a/t/pt-online-schema-change/rename_self_ref_fk_constraints.t b/t/pt-online-schema-change/rename_self_ref_fk_constraints.t
new file mode 100644
index 00000000..4b56d000
--- /dev/null
+++ b/t/pt-online-schema-change/rename_self_ref_fk_constraints.t
@@ -0,0 +1,113 @@
+#!/usr/bin/env perl
+
+BEGIN {
+   die "The PERCONA_TOOLKIT_BRANCH environment variable is not set.\n"
+      unless $ENV{PERCONA_TOOLKIT_BRANCH} && -d $ENV{PERCONA_TOOLKIT_BRANCH};
+   unshift @INC, "$ENV{PERCONA_TOOLKIT_BRANCH}/lib";
+};
+
+use strict;
+use warnings FATAL => 'all';
+use English qw(-no_match_vars);
+use Test::More;
+
+use Data::Dumper;
+use PerconaTest;
+use Sandbox;
+
+require "$trunk/bin/pt-online-schema-change";
+
+my $dp = new DSNParser(opts=>$dsn_opts);
+my $sb = new Sandbox(basedir => '/tmp', DSNParser => $dp);
+my $master_dbh = $sb->get_dbh_for('master');
+
+if ( !$master_dbh ) {
+   plan skip_all => 'Cannot connect to sandbox master';
+}
+
+# The sandbox servers run with lock_wait_timeout=3 and it's not dynamic
+# so we need to specify --set-vars innodb_lock_wait_timeout-3 else the
+# tool will die.
+my $master_dsn = 'h=127.1,P=12345,u=msandbox,p=msandbox';
+my @args       = (qw(--set-vars innodb_lock_wait_timeout=3 --alter-foreign-keys-method rebuild_constraints));
+my $output;
+my $exit_status;
+my $sample  = "t/pt-online-schema-change/samples/";
+
+# ############################################################################
+# https://bugs.launchpad.net/percona-toolkit/+bug/1632522
+# pt-online-schema-change fails with duplicate key in table for self-referencing FK
+# ############################################################################
+
+$sb->load_file('master', "$sample/bug-1632522.sql");
+
+# run once: we expect the constraint name to be appended with one underscore
+# but the self-referencing constraint will have 2 underscore
+($output, $exit_status) = full_output(
+   sub { pt_online_schema_change::main(@args,
+      "$master_dsn,D=bug1632522,t=test_table",
+      "--alter", "ENGINE=InnoDB",
+      qw(--execute)) },
+);
+
+my $constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1632522' and (TABLE_NAME='test_table' OR TABLE_NAME='person') and CONSTRAINT_NAME LIKE '%fk_%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
+
+is_deeply(
+   $constraints,
+   [
+      ['person', '_fk_testId'],
+      ['test_table', '_fk_person'],
+      ['test_table', '__fk_refId'],
+   ],
+   "First run adds or removes underscore from constraint names, accordingly"
+);
+
+# run second time: we expect constraint names to be prefixed with one underscore
+# if they havre't one, and to remove 2 if they have 2
+($output, $exit_status) = full_output(
+   sub { pt_online_schema_change::main(@args,
+      "$master_dsn,D=bug1632522,t=test_table",
+      "--alter", "ENGINE=InnoDB",
+      qw(--execute)) },
+);
+
+$constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1632522' and (TABLE_NAME='test_table' OR TABLE_NAME='person') and CONSTRAINT_NAME LIKE '%fk_%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
+
+
+is_deeply(
+   $constraints,
+   [
+      ['person', '__fk_testId'],
+      ['test_table', '_fk_refId'],
+      ['test_table', '__fk_person'],
+   ],
+   "Second run self-referencing will be one due to rebuild_constraints"
+);
+
+# run third time: we expect constraints to be the same as we started (toggled back)
+($output, $exit_status) = full_output(
+   sub { pt_online_schema_change::main(@args,
+      "$master_dsn,D=bug1632522,t=test_table",
+      "--alter", "ENGINE=InnoDB",
+      qw(--execute)) },
+);
+
+$constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1632522' and (TABLE_NAME='test_table' OR TABLE_NAME='person') and CONSTRAINT_NAME LIKE '%fk_%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
+
+
+is_deeply(
+   $constraints,
+   [
+      ['person', 'fk_testId'],
+      ['test_table', 'fk_person'],
+      ['test_table', 'fk_refId'],
+   ],
+   "Third run toggles constraint names back to how they were"
+);
+
+# #############################################################################
+# Done.
+# #############################################################################
+$sb->wipe_clean($master_dbh);
+ok($sb->ok(), "Sandbox servers") or BAIL_OUT(__FILE__ . " broke the sandbox");
+done_testing;
diff --git a/t/pt-online-schema-change/samples/bug-1632522.sql b/t/pt-online-schema-change/samples/bug-1632522.sql
new file mode 100644
index 00000000..87ff3501
--- /dev/null
+++ b/t/pt-online-schema-change/samples/bug-1632522.sql
@@ -0,0 +1,25 @@
+-- Setup database and test tables with self referencing FK
+
+drop database if exists bug1632522;
+create database bug1632522;
+use bug1632522;
+
+CREATE TABLE `person` (
+ `id` bigint(20) NOT NULL AUTO_INCREMENT,
+ `name` varchar(20) NOT NULL,
+ `testId` bigint(20) DEFAULT NULL,
+ PRIMARY KEY (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+
+CREATE TABLE `test_table` (
+  `id` bigint(20) NOT NULL AUTO_INCREMENT,
+  `refId` bigint(20) DEFAULT NULL,
+  `person` bigint(20) DEFAULT NULL,
+  PRIMARY KEY (`id`),
+  KEY `fk_person` (`person`),
+  KEY `fk_refId` (`refId`),
+  CONSTRAINT `fk_person` FOREIGN KEY (`person`) REFERENCES `person` (`id`),
+  CONSTRAINT `fk_refId` FOREIGN KEY (`refId`) REFERENCES `test_table` (`id`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8;
+
+ALTER TABLE `person` ADD CONSTRAINT `fk_testId` FOREIGN KEY (`testId`) REFERENCES `test_table` (`id`);