diff --git a/mysql-test/suite/innodb/include/alter_table_pk_no_sort.inc b/mysql-test/suite/innodb/include/alter_table_pk_no_sort.inc
index 6a2fcd15be0..61e304a7626 100644
--- a/mysql-test/suite/innodb/include/alter_table_pk_no_sort.inc
+++ b/mysql-test/suite/innodb/include/alter_table_pk_no_sort.inc
@@ -263,3 +263,10 @@ create table t1(o1 int, o2 int, o3 int, primary key(o1,o2,o3)) engine = innodb;
 insert into t1 values(1,1,2),(2,2,1);
 alter table t1 drop primary key, add primary key(o1), lock=none;
 drop table t1;
+
+# pk(o1,o2) to pk(o1,o2,autoinc) must not sort
+create table t1(o1 int, o2 int, primary key(o1,o2)) engine = innodb;
+insert into t1 values(1,1),(2,1);
+alter table t1 drop primary key, add column a int unique auto_increment,
+add primary key(o1,o2,a), algorithm=inplace;
+drop table t1;
diff --git a/mysql-test/suite/innodb/r/alter_table.result b/mysql-test/suite/innodb/r/alter_table.result
index e47bfb90152..94262ac29c3 100644
--- a/mysql-test/suite/innodb/r/alter_table.result
+++ b/mysql-test/suite/innodb/r/alter_table.result
@@ -53,3 +53,10 @@ ALTER TABLE t1 DROP a;
 ERROR HY000: Cannot drop index 'a': needed in a foreign key constraint
 ALTER TABLE t1 ADD c INT;
 DROP TABLE t1, tx;
+#
+# MDEV-14119 Assertion cmp_rec_rec() on ALTER TABLE
+#
+CREATE TABLE t1(a INT NOT NULL UNIQUE) ENGINE=InnoDB;
+INSERT INTO t1 SELECT * FROM seq_1_to_128;
+ALTER TABLE t1 ADD b TINYINT AUTO_INCREMENT PRIMARY KEY, DROP KEY a;
+DROP TABLE t1;
diff --git a/mysql-test/suite/innodb/r/innodb-index-debug.result b/mysql-test/suite/innodb/r/innodb-index-debug.result
index b1f8c9ad3cc..bf2abce989c 100644
--- a/mysql-test/suite/innodb/r/innodb-index-debug.result
+++ b/mysql-test/suite/innodb/r/innodb-index-debug.result
@@ -323,4 +323,9 @@ create table t1(o1 int, o2 int, o3 int, primary key(o1,o2,o3)) engine = innodb;
 insert into t1 values(1,1,2),(2,2,1);
 alter table t1 drop primary key, add primary key(o1), lock=none;
 drop table t1;
+create table t1(o1 int, o2 int, primary key(o1,o2)) engine = innodb;
+insert into t1 values(1,1),(2,1);
+alter table t1 drop primary key, add column a int unique auto_increment,
+add primary key(o1,o2,a), algorithm=inplace;
+drop table t1;
 SET DEBUG_DBUG = @saved_debug_dbug;
diff --git a/mysql-test/suite/innodb/r/innodb-index.result b/mysql-test/suite/innodb/r/innodb-index.result
index bdc16ad7692..5e91efb7062 100644
--- a/mysql-test/suite/innodb/r/innodb-index.result
+++ b/mysql-test/suite/innodb/r/innodb-index.result
@@ -1903,6 +1903,11 @@ create table t1(o1 int, o2 int, o3 int, primary key(o1,o2,o3)) engine = innodb;
 insert into t1 values(1,1,2),(2,2,1);
 alter table t1 drop primary key, add primary key(o1), lock=none;
 drop table t1;
+create table t1(o1 int, o2 int, primary key(o1,o2)) engine = innodb;
+insert into t1 values(1,1),(2,1);
+alter table t1 drop primary key, add column a int unique auto_increment,
+add primary key(o1,o2,a), algorithm=inplace;
+drop table t1;
 #
 # MDEV-15325 Incomplete validation of missing tablespace during recovery
 #
diff --git a/mysql-test/suite/innodb/t/alter_table.test b/mysql-test/suite/innodb/t/alter_table.test
index d0943e7d407..6bc30d2e8ee 100644
--- a/mysql-test/suite/innodb/t/alter_table.test
+++ b/mysql-test/suite/innodb/t/alter_table.test
@@ -1,4 +1,5 @@
 --source include/have_innodb.inc
+--source include/have_sequence.inc
 #
 # MDEV-11995 ALTER TABLE proceeds despite reporting ER_TOO_LONG_KEY error
 #
@@ -59,3 +60,11 @@ ALTER TABLE t1 ADD b INT;
 ALTER TABLE t1 DROP a;
 ALTER TABLE t1 ADD c INT;
 DROP TABLE t1, tx;
+
+--echo #
+--echo # MDEV-14119 Assertion cmp_rec_rec() on ALTER TABLE
+--echo #
+CREATE TABLE t1(a INT NOT NULL UNIQUE) ENGINE=InnoDB;
+INSERT INTO t1 SELECT * FROM seq_1_to_128;
+ALTER TABLE t1 ADD b TINYINT AUTO_INCREMENT PRIMARY KEY, DROP KEY a;
+DROP TABLE t1;
diff --git a/storage/innobase/handler/handler0alter.cc b/storage/innobase/handler/handler0alter.cc
index 782b0d9efb2..0f5ac81f663 100644
--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -3362,7 +3362,11 @@ innobase_pk_order_preserved(
 		if (old_pk_column) {
 			new_field_order = old_field;
 		} else if (innobase_pk_col_is_existing(new_col_no, col_map,
-						       old_n_cols)) {
+						       old_n_cols)
+			   || new_clust_index->table->persistent_autoinc
+			   == new_field + 1) {
+			/* Adding an existing column or an AUTO_INCREMENT
+			column may change the existing ordering. */
 			new_field_order = old_n_uniq + existing_field_count++;
 		} else {
 			/* Skip newly added column. */
@@ -4913,12 +4917,6 @@ index_created:
 			user_table);
 		dict_index_t*	new_clust_index = dict_table_get_first_index(
 			ctx->new_table);
-		ctx->skip_pk_sort = innobase_pk_order_preserved(
-			ctx->col_map, clust_index, new_clust_index);
-
-		DBUG_EXECUTE_IF("innodb_alter_table_pk_assert_no_sort",
-			DBUG_ASSERT(ctx->skip_pk_sort););
-
 		DBUG_ASSERT(!ctx->new_table->persistent_autoinc);
 		if (const Field* ai = altered_table->found_next_number_field) {
 			const unsigned	col_no = innodb_col_no(ai);
@@ -4937,6 +4935,12 @@ index_created:
 			}
 		}
 
+		ctx->skip_pk_sort = innobase_pk_order_preserved(
+			ctx->col_map, clust_index, new_clust_index);
+
+		DBUG_EXECUTE_IF("innodb_alter_table_pk_assert_no_sort",
+			DBUG_ASSERT(ctx->skip_pk_sort););
+
 		if (ctx->online) {
 			/* Allocate a log for online table rebuild. */
 			rw_lock_x_lock(&clust_index->lock);