diff --git a/mysql-test/r/lock_multi_bug38499.result b/mysql-test/r/lock_multi_bug38499.result
new file mode 100644
index 00000000000..fd0f2138a8d
--- /dev/null
+++ b/mysql-test/r/lock_multi_bug38499.result
@@ -0,0 +1,19 @@
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1( a INT, b INT );
+INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3), (4, 4);
+# 1. test regular tables
+# 1.1. test altering of columns that multiupdate doesn't use
+# 1.1.1. normal mode
+# 1.1.2. PS mode
+# 1.2. test altering of columns that multiupdate uses
+# 1.2.1. normal mode
+# 1.2.2. PS mode
+ALTER TABLE t1 ADD COLUMN a INT;
+# 2. test UNIONs
+# 2.1. test altering of columns that multiupdate doesn't use
+# 2.1.1. normal mode
+# 2.1.2. PS mode
+# 2.2. test altering of columns that multiupdate uses
+# 2.2.1. normal mode
+# 2.2.2. PS mode
+DROP TABLE t1;
diff --git a/mysql-test/r/lock_multi_bug38691.result b/mysql-test/r/lock_multi_bug38691.result
new file mode 100644
index 00000000000..74b9603d8e3
--- /dev/null
+++ b/mysql-test/r/lock_multi_bug38691.result
@@ -0,0 +1,17 @@
+DROP TABLE IF EXISTS t1,t2,t3;
+CREATE TABLE t1 (
+a int(11) unsigned default NULL,
+b varchar(255) default NULL,
+UNIQUE KEY a (a),
+KEY b (b)
+);
+INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3);
+CREATE TABLE t2 SELECT * FROM t1;
+CREATE TABLE t3 SELECT * FROM t1;
+# test altering of columns that multiupdate doesn't use
+# normal mode
+# PS mode
+# test altering of columns that multiupdate uses
+# normal mode
+# PS mode
+DROP TABLE t1, t2, t3;
diff --git a/mysql-test/t/lock_multi.test b/mysql-test/t/lock_multi.test
index e3a577127fa..6c3c942b046 100644
--- a/mysql-test/t/lock_multi.test
+++ b/mysql-test/t/lock_multi.test
@@ -84,8 +84,6 @@ insert into t1 values(2,2);
 insert into t2 values(1,2);
 lock table t1 read;
 connection writer;
-# mleich: IMHO the "send is not necessary because the update should not block.
-#         But it will save some runtime in case we block because of an error.
 send
 update t1,t2 set c=a where b=d;
 connection reader;
@@ -191,8 +189,8 @@ connection locker;
 USE mysql;
 LOCK TABLES columns_priv WRITE, db WRITE, host WRITE, user WRITE;
 FLUSH TABLES;
---sleep 1
-#
+
+
 connection reader;
 USE mysql;
 # Note:  This must be a multi-table select, otherwise the deadlock will not occur
diff --git a/mysql-test/t/lock_multi_bug38499.test b/mysql-test/t/lock_multi_bug38499.test
new file mode 100644
index 00000000000..8178987e802
--- /dev/null
+++ b/mysql-test/t/lock_multi_bug38499.test
@@ -0,0 +1,221 @@
+# Bug38499 flush tables and multitable table update with derived table cause crash
+# MySQL >= 5.0
+#
+
+# Save the initial number of concurrent sessions
+--source include/count_sessions.inc
+
+connect (locker,localhost,root,,);
+connect (writer,localhost,root,,);
+
+--connection default
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+CREATE TABLE t1( a INT, b INT );
+INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3), (4, 4);
+
+--echo # 1. test regular tables
+--echo # 1.1. test altering of columns that multiupdate doesn't use
+--echo # 1.1.1. normal mode
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+--dec $i
+
+--connection writer
+  send UPDATE t1, (SELECT 1 FROM t1 t1i) d SET a = 0 WHERE 1=0;
+
+--connection locker
+  ALTER TABLE t1 ADD COLUMN (c INT);
+  ALTER TABLE t1 DROP COLUMN c;
+
+--connection writer
+--reap
+}
+
+--echo # 1.1.2. PS mode
+
+--connection writer
+PREPARE stmt FROM 'UPDATE t1, (SELECT 1 FROM t1 t1i) d SET a = 0 WHERE 1=0';
+
+let $i = 100;
+while ($i) {
+--dec $i
+
+--connection writer
+--send EXECUTE stmt
+
+--connection locker
+  ALTER TABLE t1 ADD COLUMN (c INT);
+  ALTER TABLE t1 DROP COLUMN c;
+
+--connection writer
+--reap
+}
+--enable_query_log
+
+--echo # 1.2. test altering of columns that multiupdate uses
+--echo # 1.2.1. normal mode
+
+--connection default
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+  dec $i;
+
+--connection locker
+--error 0,ER_DUP_FIELDNAME
+  ALTER TABLE t1 ADD COLUMN a int(11) unsigned default NULL;
+  UPDATE t1 SET a=b;
+
+--connection writer
+--send UPDATE t1, (SELECT 1 FROM t1 t1i) d SET a = 0 WHERE 1=0;
+
+--connection locker
+--error 0,ER_CANT_DROP_FIELD_OR_KEY
+  ALTER TABLE t1 DROP COLUMN a;
+
+--connection writer
+--error 0,ER_BAD_FIELD_ERROR # unknown column error
+--reap
+}
+--enable_query_log
+
+--echo # 1.2.2. PS mode
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+  dec $i;
+
+--connection locker
+--error 0,ER_DUP_FIELDNAME
+  ALTER TABLE t1 ADD COLUMN a INT;
+  UPDATE t1 SET a=b;
+
+--connection writer
+  PREPARE stmt FROM 'UPDATE t1, (SELECT 1 FROM t1 t1i) d SET a = 0 WHERE 1=0';
+--send EXECUTE stmt
+
+--connection locker
+--error 0,ER_CANT_DROP_FIELD_OR_KEY
+  ALTER TABLE t1 DROP COLUMN a;
+
+--connection writer
+--error 0,ER_BAD_FIELD_ERROR # Unknown column 'a' in 'field list'
+--reap
+}
+--enable_query_log
+--connection default
+ALTER TABLE t1 ADD COLUMN a INT;
+
+--echo # 2. test UNIONs
+--echo # 2.1. test altering of columns that multiupdate doesn't use
+--echo # 2.1.1. normal mode
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+--dec $i
+
+--connection writer
+  send UPDATE t1, ((SELECT 1 FROM t1 t1i) UNION (SELECT 2 FROM t1 t1ii)) e SET a = 0 WHERE 1=0;
+
+--connection locker
+  ALTER TABLE t1 ADD COLUMN (c INT);
+  ALTER TABLE t1 DROP COLUMN c;
+
+--connection writer
+--reap
+}
+
+--echo # 2.1.2. PS mode
+
+--connection writer
+PREPARE stmt FROM 'UPDATE t1, ((SELECT 1 FROM t1 t1i) UNION (SELECT 2 FROM t1 t1ii)) e SET a = 0 WHERE 1=0';
+
+let $i = 100;
+while ($i) {
+--dec $i
+
+--connection writer
+--send EXECUTE stmt
+
+--connection locker
+  ALTER TABLE t1 ADD COLUMN (c INT);
+  ALTER TABLE t1 DROP COLUMN c;
+
+--connection writer
+--reap
+}
+--enable_query_log
+
+--echo # 2.2. test altering of columns that multiupdate uses
+--echo # 2.2.1. normal mode
+
+--connection default
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+  dec $i;
+
+--connection locker
+--error 0,ER_DUP_FIELDNAME
+  ALTER TABLE t1 ADD COLUMN a int(11) unsigned default NULL;
+  UPDATE t1 SET a=b;
+
+--connection writer
+--send UPDATE t1, ((SELECT 1 FROM t1 t1i) UNION (SELECT 2 FROM t1 t1ii)) e SET a = 0 WHERE 1=0;
+
+--connection locker
+--error 0,ER_CANT_DROP_FIELD_OR_KEY
+  ALTER TABLE t1 DROP COLUMN a;
+
+--connection writer
+--error 0,ER_BAD_FIELD_ERROR # Unknown column 'a' in 'field list'
+--reap
+}
+--enable_query_log
+
+--echo # 2.2.2. PS mode
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+  dec $i;
+
+--connection locker
+--error 0,ER_DUP_FIELDNAME
+  ALTER TABLE t1 ADD COLUMN a INT;
+  UPDATE t1 SET a=b;
+
+--connection writer
+  PREPARE stmt FROM 'UPDATE t1, ((SELECT 1 FROM t1 t1i) UNION (SELECT 2 FROM t1 t1ii)) e SET a = 0 WHERE 1=0';
+--send EXECUTE stmt
+
+--connection locker
+--error 0,ER_CANT_DROP_FIELD_OR_KEY
+  ALTER TABLE t1 DROP COLUMN a;
+
+--connection writer
+--error 0,ER_BAD_FIELD_ERROR # Unknown column 'a' in 'field list'
+--reap
+}
+--enable_query_log
+--connection default
+DROP TABLE t1;
+
+
+# Close connections
+--disconnect locker
+--disconnect writer
+
+# End of 5.0 tests
+
+# Wait till all disconnects are completed
+--source include/wait_until_count_sessions.inc
+
diff --git a/mysql-test/t/lock_multi_bug38691.test b/mysql-test/t/lock_multi_bug38691.test
new file mode 100644
index 00000000000..0458f31579e
--- /dev/null
+++ b/mysql-test/t/lock_multi_bug38691.test
@@ -0,0 +1,141 @@
+#
+# Bug#38691 segfault/abort in ``UPDATE ...JOIN'' while
+#           ``FLUSH TABLES WITH READ LOCK''
+# MySQL >= 5.0
+#
+
+
+# Save the initial number of concurrent sessions
+--source include/count_sessions.inc
+
+# Test to see if select will get the lock ahead of low priority update
+
+connect (locker,localhost,root,,);
+connect (writer,localhost,root,,);
+
+--connection default
+--disable_warnings
+DROP TABLE IF EXISTS t1,t2,t3;
+--enable_warnings
+
+CREATE TABLE t1 (
+  a int(11) unsigned default NULL,
+  b varchar(255) default NULL,
+  UNIQUE KEY a (a),
+  KEY b (b)
+);
+
+INSERT INTO t1 VALUES (1, 1), (2, 2), (3, 3);
+CREATE TABLE t2 SELECT * FROM t1;
+CREATE TABLE t3 SELECT * FROM t1;
+
+--echo # test altering of columns that multiupdate doesn't use
+
+--echo # normal mode
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+--dec $i
+
+--connection writer
+  send UPDATE t2 INNER JOIN (t1 JOIN t3 USING(a)) USING(a)
+         SET a = NULL WHERE t1.b <> t2.b;
+
+--connection locker
+  ALTER TABLE t2 ADD COLUMN (c INT);
+  ALTER TABLE t2 DROP COLUMN c;
+
+--connection writer
+--reap
+}
+
+--echo # PS mode
+
+--connection writer
+PREPARE stmt FROM 'UPDATE t2 INNER JOIN (t1 JOIN t3 USING(a)) USING(a)
+                     SET a = NULL WHERE t1.b <> t2.b';
+
+let $i = 100;
+while ($i) {
+--dec $i
+
+--connection writer
+--send EXECUTE stmt
+
+--connection locker
+  ALTER TABLE t2 ADD COLUMN (c INT);
+  ALTER TABLE t2 DROP COLUMN c;
+
+--connection writer
+--reap
+}
+--enable_query_log
+
+
+--echo # test altering of columns that multiupdate uses
+
+--echo # normal mode
+
+--connection default
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+  dec $i;
+
+--connection locker
+--error 0,ER_DUP_FIELDNAME
+  ALTER TABLE t2 ADD COLUMN a int(11) unsigned default NULL;
+  UPDATE t2 SET a=b;
+
+--connection writer
+--send UPDATE t2 INNER JOIN (t1 JOIN t3 USING(a)) USING(a) SET a = NULL WHERE t1.b <> t2.b
+
+--connection locker
+--error 0,ER_CANT_DROP_FIELD_OR_KEY
+  ALTER TABLE t2 DROP COLUMN a;
+
+--connection writer
+--error 0,ER_BAD_FIELD_ERROR
+--reap
+}
+--enable_query_log
+
+--echo # PS mode
+
+--disable_query_log
+let $i = 100;
+while ($i) {
+  dec $i;
+
+--connection locker
+--error 0,ER_DUP_FIELDNAME
+  ALTER TABLE t2 ADD COLUMN a int(11) unsigned default NULL;
+  UPDATE t2 SET a=b;
+
+--connection writer
+  PREPARE stmt FROM 'UPDATE t2 INNER JOIN (t1 JOIN t3 USING(a)) USING(a) SET a = NULL WHERE t1.b <> t2.b';
+--send EXECUTE stmt
+
+--connection locker
+--error 0,ER_CANT_DROP_FIELD_OR_KEY
+  ALTER TABLE t2 DROP COLUMN a;
+
+--connection writer
+--error 0,ER_BAD_FIELD_ERROR
+--reap
+
+}
+--enable_query_log
+--connection default
+DROP TABLE t1, t2, t3;
+
+
+# Close connections
+--disconnect locker
+--disconnect writer
+
+# Wait till all disconnects are completed
+--source include/wait_until_count_sessions.inc
+