diff --git a/include/myisamchk.h b/include/myisamchk.h
index 5876d67ca5f..eaff2c9ffdd 100644
--- a/include/myisamchk.h
+++ b/include/myisamchk.h
@@ -117,6 +117,7 @@ typedef struct st_handler_check_param
   uint progress_counter;             /* How often to call _report_progress() */
   ulonglong progress, max_progress;
 
+  void (*init_fix_record)(void *);
   int (*fix_record)(struct st_myisam_info *info, uchar *record, int keynum);
 
   mysql_mutex_t print_msg_mutex;
diff --git a/mysql-test/suite/vcol/r/vcol_keys_myisam.result b/mysql-test/suite/vcol/r/vcol_keys_myisam.result
index cbee8b733ed..74d733948af 100644
--- a/mysql-test/suite/vcol/r/vcol_keys_myisam.result
+++ b/mysql-test/suite/vcol/r/vcol_keys_myisam.result
@@ -418,3 +418,40 @@ create or replace table t2 (pk int, b int, c int as (b) virtual, primary key (pk
 insert into t2 (pk) select a from t1;
 ERROR 23000: Duplicate entry '1' for key 'PRIMARY'
 drop tables t1, t2;
+#
+# MDEV-23294 Segfault or assertion upon MyISAM repair
+#
+set @old_mode= @@sql_mode;
+set @old_myisam_repair_threads= @@myisam_repair_threads;
+set sql_mode='', myisam_repair_threads=2;
+create table t (a binary,b blob,c blob as (concat (a,b)),h char,index (c)) engine=innodb;
+Warnings:
+Warning	1286	Unknown storage engine 'innodb'
+Warning	1266	Using storage engine MyISAM for table 't'
+Note	1071	Specified key was too long; max key length is 1000 bytes
+insert into t values (0,0,default,0);
+create table ti like t;
+alter table ti engine=myisam;
+insert into ti select * from t;
+Warnings:
+Warning	1906	The value specified for generated column 'c' in table 'ti' has been ignored
+drop tables ti, t;
+create table t (id int,a varchar(1),b varchar(1),c varchar(1) generated always as (concat (a,b)),key(c)) engine=myisam;
+insert into t values (0,0,9687,0);
+Warnings:
+Warning	1265	Data truncated for column 'b' at row 1
+Warning	1906	The value specified for generated column 'c' in table 't' has been ignored
+Warning	1265	Data truncated for column 'c' at row 1
+repair table t quick;
+Table	Op	Msg_type	Msg_text
+test.t	repair	status	OK
+drop table t;
+create table t1 (b varchar(1024), c char(3), unique(b,c)) engine=myisam;
+insert into t1 values ('foo','baz');
+alter table t1 disable keys;
+set session myisam_repair_threads= 2;
+insert into t1 select 'qux';
+ERROR 21S01: Column count doesn't match value count at row 1
+drop table t1;
+set sql_mode= @old_mode;
+set myisam_repair_threads= @old_myisam_repair_threads;
diff --git a/mysql-test/suite/vcol/t/vcol_keys_myisam.test b/mysql-test/suite/vcol/t/vcol_keys_myisam.test
index 2a5aa3cd479..724cb8e510c 100644
--- a/mysql-test/suite/vcol/t/vcol_keys_myisam.test
+++ b/mysql-test/suite/vcol/t/vcol_keys_myisam.test
@@ -313,3 +313,32 @@ create or replace table t2 (pk int, b int, c int as (b) virtual, primary key (pk
 --error ER_DUP_ENTRY
 insert into t2 (pk) select a from t1;
 drop tables t1, t2;
+
+--echo #
+--echo # MDEV-23294 Segfault or assertion upon MyISAM repair
+--echo #
+set @old_mode= @@sql_mode;
+set @old_myisam_repair_threads= @@myisam_repair_threads;
+set sql_mode='', myisam_repair_threads=2;
+create table t (a binary,b blob,c blob as (concat (a,b)),h char,index (c)) engine=innodb;
+insert into t values (0,0,default,0);
+create table ti like t;
+alter table ti engine=myisam;
+insert into ti select * from t;
+drop tables ti, t;
+
+create table t (id int,a varchar(1),b varchar(1),c varchar(1) generated always as (concat (a,b)),key(c)) engine=myisam;
+insert into t values (0,0,9687,0);
+repair table t quick;
+drop table t;
+
+create table t1 (b varchar(1024), c char(3), unique(b,c)) engine=myisam;
+insert into t1 values ('foo','baz');
+alter table t1 disable keys;
+set session myisam_repair_threads= 2;
+--error ER_WRONG_VALUE_COUNT_ON_ROW
+insert into t1 select 'qux';
+# cleanup
+drop table t1;
+set sql_mode= @old_mode;
+set myisam_repair_threads= @old_myisam_repair_threads;
diff --git a/storage/myisam/ha_myisam.cc b/storage/myisam/ha_myisam.cc
index ddab8bcf741..0db7179e7e9 100644
--- a/storage/myisam/ha_myisam.cc
+++ b/storage/myisam/ha_myisam.cc
@@ -709,6 +709,16 @@ my_bool mi_killed_in_mariadb(MI_INFO *info)
   return (((TABLE*) (info->external_ref))->in_use->killed != 0);
 }
 
+static void init_compute_vcols(void *table)
+{
+  /*
+    To evaluate vcols we must have current_thd set.
+    This will set current_thd in all threads to the same THD, but it's
+    safe, because vcols are always evaluated under info->s->intern_lock.
+  */
+  set_current_thd(static_cast<TABLE *>(table)->in_use);
+}
+
 static int compute_vcols(MI_INFO *info, uchar *record, int keynum)
 {
   /* This mutex is needed for parallel repair */
@@ -1010,6 +1020,7 @@ void ha_myisam::setup_vcols_for_repair(HA_CHECK *param)
   }
   DBUG_ASSERT(file->s->base.reclength < file->s->vreclength ||
               !table->s->stored_fields);
+  param->init_fix_record= init_compute_vcols;
   param->fix_record= compute_vcols;
   table->use_all_columns();
 }
diff --git a/storage/myisam/sort.c b/storage/myisam/sort.c
index e586543363b..f4729f75895 100644
--- a/storage/myisam/sort.c
+++ b/storage/myisam/sort.c
@@ -503,6 +503,11 @@ pthread_handler_t thr_find_all_keys(void *arg)
 {
   MI_SORT_PARAM *sort_param= (MI_SORT_PARAM*) arg;
   my_bool error= FALSE;
+
+  MI_SORT_INFO *si= sort_param->sort_info;
+  if (si->param->init_fix_record)
+    si->param->init_fix_record(si->info->external_ref);
+
   /* If my_thread_init fails */
   if (my_thread_init() || thr_find_all_keys_exec(sort_param))
     error= TRUE;