diff --git a/mysql-test/main/alter_table_online.result b/mysql-test/main/alter_table_online.result
index 903fa86de94..a0850b0b8fc 100644
--- a/mysql-test/main/alter_table_online.result
+++ b/mysql-test/main/alter_table_online.result
@@ -1,4 +1,11 @@
 #
+# alter ignore cannot be done online
+#
+create table t (a int);
+alter ignore table t add primary key (a), algorithm=copy, lock=none;
+ERROR 0A000: LOCK=NONE is not supported. Reason: COPY algorithm requires a lock. Try LOCK=SHARED
+drop table t;
+#
 # MDEV-28771 Assertion `table->in_use&&tdc->flushed' failed after ALTER
 #
 create table t (a char(1));
diff --git a/mysql-test/main/alter_table_online.test b/mysql-test/main/alter_table_online.test
index 92710f46cbf..03cd78084fd 100644
--- a/mysql-test/main/alter_table_online.test
+++ b/mysql-test/main/alter_table_online.test
@@ -1,6 +1,14 @@
 --source include/binlog_combinations.inc
 --source include/have_innodb.inc
 
+--echo #
+--echo # alter ignore cannot be done online
+--echo #
+create table t (a int);
+--error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON
+alter ignore table t add primary key (a), algorithm=copy, lock=none;
+drop table t;
+
 --echo #
 --echo # MDEV-28771 Assertion `table->in_use&&tdc->flushed' failed after ALTER
 --echo #
diff --git a/mysql-test/main/alter_table_online_debug.result b/mysql-test/main/alter_table_online_debug.result
index ee4772dc289..9f33fba4b52 100644
--- a/mysql-test/main/alter_table_online_debug.result
+++ b/mysql-test/main/alter_table_online_debug.result
@@ -654,8 +654,9 @@ create table t1 (a char(9), b char(9) as (a) stored);
 insert into t1(a) values ('foobar');
 set debug_sync= 'now wait_for downgraded';
 connection con2;
+set sql_mode='';
 set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
-alter ignore table t1 drop b, add b char(3) as (a) stored, algorithm=copy, lock=none;
+alter table t1 drop b, add b char(3) as (a) stored, algorithm=copy, lock=none;
 connection default;
 update t1 set a = 'foobarqux';
 set debug_sync= 'now signal goforit';
@@ -663,6 +664,7 @@ connection con2;
 Warnings:
 Warning	1265	Data truncated for column 'b' at row 1
 Warning	1265	Data truncated for column 'b' at row 2
+set sql_mode=default;
 connection default;
 drop table t1;
 set debug_sync= reset;
diff --git a/mysql-test/main/alter_table_online_debug.test b/mysql-test/main/alter_table_online_debug.test
index 26fe2d12e8f..db40f3c5650 100644
--- a/mysql-test/main/alter_table_online_debug.test
+++ b/mysql-test/main/alter_table_online_debug.test
@@ -810,8 +810,9 @@ insert into t1(a) values ('foobar');
 --send set debug_sync= 'now wait_for downgraded'
 
 --connection con2
+set sql_mode='';
 set debug_sync= 'alter_table_online_downgraded signal downgraded wait_for goforit';
---send alter ignore table t1 drop b, add b char(3) as (a) stored, algorithm=copy, lock=none
+--send alter table t1 drop b, add b char(3) as (a) stored, algorithm=copy, lock=none
 
 --connection default
 --reap
@@ -820,6 +821,7 @@ set debug_sync= 'now signal goforit';
 
 --connection con2
 --reap
+set sql_mode=default;
 --connection default
 drop table t1;
 set debug_sync= reset;
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index f7dc348229f..9bcfd304f4e 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -10029,6 +10029,7 @@ bool mysql_alter_table(THD *thd, const LEX_CSTRING *new_db,
   if (alter_info->requested_lock > Alter_info::ALTER_TABLE_LOCK_NONE
       || alter_info->flags & ALTER_DROP_SYSTEM_VERSIONING
       || thd->lex->sql_command == SQLCOM_OPTIMIZE
+      || ignore
       || alter_info->algorithm(thd) > Alter_info::ALTER_TABLE_ALGORITHM_COPY)
     online= false;