diff --git a/localtests/alter-charset/create.sql b/localtests/alter-charset/create.sql
new file mode 100644
index 0000000..e2861d1
--- /dev/null
+++ b/localtests/alter-charset/create.sql
@@ -0,0 +1,23 @@
+drop table if exists gh_ost_test;
+create table gh_ost_test (
+  id int auto_increment,
+  t varchar(128)  charset latin1 collate latin1_swedish_ci,
+  tutf8 varchar(128) charset utf8,
+  tutf8mb4 varchar(128) charset utf8mb4,
+  primary key(id)
+) auto_increment=1;
+
+drop event if exists gh_ost_test;
+delimiter ;;
+create event gh_ost_test
+  on schedule every 1 second
+  starts current_timestamp
+  ends current_timestamp + interval 60 second
+  on completion not preserve
+  enable
+  do
+begin
+  insert into gh_ost_test values (null, md5(rand()), md5(rand()), md5(rand()));
+  insert into gh_ost_test values (null, 'átesting', 'átesting', 'átesting');
+  insert into gh_ost_test values (null, 'testátest', 'testátest', '🍻😀');
+end ;;
diff --git a/localtests/alter-charset/extra_args b/localtests/alter-charset/extra_args
new file mode 100644
index 0000000..29e526e
--- /dev/null
+++ b/localtests/alter-charset/extra_args
@@ -0,0 +1 @@
+--alter='MODIFY `t` varchar(128) CHARACTER SET utf8mb4 NOT NULL'