diff --git a/mysql-test/suite/vcol/r/vcol_syntax.result b/mysql-test/suite/vcol/r/vcol_syntax.result
index 1c3a7566f48..615b7013647 100644
--- a/mysql-test/suite/vcol/r/vcol_syntax.result
+++ b/mysql-test/suite/vcol/r/vcol_syntax.result
@@ -248,3 +248,106 @@ select unix_timestamp(f), unix_timestamp(g) from t;
 unix_timestamp(f)	unix_timestamp(g)
 1	2
 drop table t;
+#
+# MDEV-40041 Assertion `fixed()' failed in Item_func_connection_id::val_int on INSERT w/ TRIGGER
+#
+create table t (c int);
+lock table t write;
+create or replace table t (a int as (connection_id()));
+create trigger a before insert on t for each row set @a:=1;
+insert into t values ('');
+Warnings:
+Warning	1906	The value specified for generated column 'a' in table 't' has been ignored
+Warning	1366	Incorrect integer value: '' for column `test`.`t`.`a` at row 1
+select a = connection_id() from t;
+a = connection_id()
+1
+unlock tables;
+drop table t;
+# Simpler variant: table and trigger exist before LOCK TABLES
+create table t1 (a int as (connection_id()));
+create trigger tr1 before insert on t1 for each row set @a:=1;
+lock table t1 write;
+insert into t1 values ('');
+Warnings:
+Warning	1906	The value specified for generated column 'a' in table 't1' has been ignored
+Warning	1366	Incorrect integer value: '' for column `test`.`t1`.`a` at row 1
+select a = connection_id() from t1;
+a = connection_id()
+1
+unlock tables;
+drop table t1;
+# Trigger writes to another locked table with session vcol
+create table t1 (a int);
+create table t2 (a int primary key, b int as (connection_id()));
+create trigger tr1 before insert on t1 for each row insert into t2 values (new.a, '');
+lock table t1 write, t2 write;
+# Trigger fires for each row
+insert into t1 values (1), (2), (3);
+select a, b = connection_id() from t2;
+a	b = connection_id()
+1	1
+2	1
+3	1
+# Duplicate key in trigger
+insert into t1 values (1);
+ERROR 23000: Duplicate entry '1' for key 'PRIMARY'
+# Direct INSERT after failed trigger, then duplicate key in trigger
+insert into t2 (a) values (4);
+select a, b = connection_id() from t2;
+a	b = connection_id()
+1	1
+2	1
+3	1
+4	1
+insert into t1 values (4);
+ERROR 23000: Duplicate entry '4' for key 'PRIMARY'
+select a, b = connection_id() from t2;
+a	b = connection_id()
+1	1
+2	1
+3	1
+4	1
+unlock tables;
+drop tables t1, t2;
+# Trigger fails, later statements use the same locked table
+create table t1 (a int as (connection_id()), b int);
+create trigger tr1 before insert on t1 for each row
+if new.b = 0 then signal sqlstate '45000'; end if|
+create trigger tr2 after insert on t1 for each row
+if new.b = -1 then signal sqlstate '45000'; end if|
+lock table t1 write;
+# BEFORE trigger fails
+insert into t1 (b) values (0);
+ERROR 45000: Unhandled user-defined exception condition
+select a = connection_id(), b from t1;
+a = connection_id()	b
+# AFTER trigger fails
+insert into t1 (b) values (-1);
+ERROR 45000: Unhandled user-defined exception condition
+select a = connection_id(), b from t1;
+a = connection_id()	b
+1	-1
+# AFTER trigger of the first row, then the second row is written
+insert into t1 values ('', 1), ('', 2);
+Warnings:
+Warning	1906	The value specified for generated column 'a' in table 't1' has been ignored
+Warning	1366	Incorrect integer value: '' for column `test`.`t1`.`a` at row 1
+Warning	1906	The value specified for generated column 'a' in table 't1' has been ignored
+Warning	1366	Incorrect integer value: '' for column `test`.`t1`.`a` at row 2
+select a = connection_id(), b from t1;
+a = connection_id()	b
+1	-1
+1	1
+1	2
+# BEFORE trigger fails after successful INSERT
+insert into t1 (b) values (0);
+ERROR 45000: Unhandled user-defined exception condition
+select a = connection_id(), b from t1;
+a = connection_id()	b
+1	-1
+1	1
+1	2
+unlock tables;
+drop table t1;
+# End of 10.11 tests
diff --git a/mysql-test/suite/vcol/t/vcol_syntax.test b/mysql-test/suite/vcol/t/vcol_syntax.test
index 4f6130a973f..aa4a85f73c0 100644
--- a/mysql-test/suite/vcol/t/vcol_syntax.test
+++ b/mysql-test/suite/vcol/t/vcol_syntax.test
@@ -197,3 +197,73 @@ flush table t;
 select unix_timestamp(f), unix_timestamp(g) from t;
 # Cleanup
 drop table t;
+
+--echo #
+--echo # MDEV-40041 Assertion `fixed()' failed in Item_func_connection_id::val_int on INSERT w/ TRIGGER
+--echo #
+create table t (c int);
+lock table t write;
+create or replace table t (a int as (connection_id()));
+create trigger a before insert on t for each row set @a:=1;
+insert into t values ('');
+select a = connection_id() from t;
+unlock tables;
+drop table t;
+
+--echo # Simpler variant: table and trigger exist before LOCK TABLES
+create table t1 (a int as (connection_id()));
+create trigger tr1 before insert on t1 for each row set @a:=1;
+lock table t1 write;
+insert into t1 values ('');
+select a = connection_id() from t1;
+unlock tables;
+drop table t1;
+
+--echo # Trigger writes to another locked table with session vcol
+create table t1 (a int);
+create table t2 (a int primary key, b int as (connection_id()));
+create trigger tr1 before insert on t1 for each row insert into t2 values (new.a, '');
+lock table t1 write, t2 write;
+--echo # Trigger fires for each row
+insert into t1 values (1), (2), (3);
+select a, b = connection_id() from t2;
+--echo # Duplicate key in trigger
+--error ER_DUP_ENTRY
+insert into t1 values (1);
+--echo # Direct INSERT after failed trigger, then duplicate key in trigger
+insert into t2 (a) values (4);
+select a, b = connection_id() from t2;
+--error ER_DUP_ENTRY
+insert into t1 values (4);
+select a, b = connection_id() from t2;
+unlock tables;
+drop tables t1, t2;
+
+--echo # Trigger fails, later statements use the same locked table
+create table t1 (a int as (connection_id()), b int);
+--delimiter |
+create trigger tr1 before insert on t1 for each row
+  if new.b = 0 then signal sqlstate '45000'; end if|
+create trigger tr2 after insert on t1 for each row
+  if new.b = -1 then signal sqlstate '45000'; end if|
+--delimiter ;
+lock table t1 write;
+--echo # BEFORE trigger fails
+--error ER_SIGNAL_EXCEPTION
+insert into t1 (b) values (0);
+select a = connection_id(), b from t1;
+--echo # AFTER trigger fails
+--error ER_SIGNAL_EXCEPTION
+insert into t1 (b) values (-1);
+select a = connection_id(), b from t1;
+--echo # AFTER trigger of the first row, then the second row is written
+insert into t1 values ('', 1), ('', 2);
+select a = connection_id(), b from t1;
+--echo # BEFORE trigger fails after successful INSERT
+--error ER_SIGNAL_EXCEPTION
+insert into t1 (b) values (0);
+select a = connection_id(), b from t1;
+unlock tables;
+drop table t1;
+
+--echo # End of 10.11 tests
diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index eabad77012a..74444752366 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -876,8 +876,11 @@ int close_thread_tables(THD *thd) noexcept
       /*
         For simple locking we cleanup it here because we don't close thread
         tables. For prelocking we close it when we do close thread tables.
+        Sub-statement does not cleanup: the outer statement may still use
+        the tables, and the top-level statement cleans up all locked tables
+        when it ends.
       */
-      if (thd->locked_tables_mode != LTM_PRELOCKED)
+      if (thd->locked_tables_mode != LTM_PRELOCKED && !thd->in_sub_stmt)
         table->vcol_cleanup_expr(thd);
     }