diff --git a/mysql-test/suite/innodb/r/innodb_mysql.result b/mysql-test/suite/innodb/r/innodb_mysql.result
index 1845b32564d..90ced3c8b16 100644
--- a/mysql-test/suite/innodb/r/innodb_mysql.result
+++ b/mysql-test/suite/innodb/r/innodb_mysql.result
@@ -2413,6 +2413,18 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	const	PRIMARY	NULL	NULL	NULL	1	Impossible ON condition
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	3	Using where
 DROP TABLE t1,t2;
+#
+# Bug#38999 valgrind warnings for update statement in function compare_record()
+#
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
+CREATE TABLE t2 (a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 values (1),(2),(3),(4),(5);
+INSERT INTO t2 values (1);
+SELECT * FROM t1 WHERE a = 2;
+a
+2
+UPDATE t1,t2 SET t1.a = t1.a + 100 WHERE t1.a = 1;
+DROP TABLE t1,t2;
 End of 5.1 tests
 #
 # Test for bug #39932 "create table fails if column for FK is in different
diff --git a/mysql-test/suite/innodb/t/innodb_mysql.test b/mysql-test/suite/innodb/t/innodb_mysql.test
index f2c770cce42..c49b215887b 100644
--- a/mysql-test/suite/innodb/t/innodb_mysql.test
+++ b/mysql-test/suite/innodb/t/innodb_mysql.test
@@ -649,6 +649,20 @@ EXPLAIN SELECT t1.id,t2.id FROM t2 LEFT JOIN t1 ON t1.id>=74 AND t1.id<=0
 
 DROP TABLE t1,t2;
 
+--echo #
+--echo # Bug#38999 valgrind warnings for update statement in function compare_record()
+--echo #
+
+CREATE TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
+CREATE TABLE t2 (a INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 values (1),(2),(3),(4),(5);
+INSERT INTO t2 values (1);
+
+SELECT * FROM t1 WHERE a = 2;
+UPDATE t1,t2 SET t1.a = t1.a + 100 WHERE t1.a = 1;
+
+DROP TABLE t1,t2;
+
 --echo End of 5.1 tests
 
 
diff --git a/storage/innobase/row/row0sel.c b/storage/innobase/row/row0sel.c
index a5bf361661b..2861235a995 100644
--- a/storage/innobase/row/row0sel.c
+++ b/storage/innobase/row/row0sel.c
@@ -2678,6 +2678,12 @@ row_sel_store_mysql_rec(
 		prebuilt->blob_heap = NULL;
 	}
 
+	/* init null bytes with default values as they might be
+	left uninitialized in some cases and these uninited bytes
+	might be copied into mysql record buffer that leads to
+	valgrind warnings */
+	memcpy(mysql_rec, prebuilt->default_rec, prebuilt->null_bitmap_len);
+
 	for (i = 0; i < prebuilt->n_template; i++) {
 
 		templ = prebuilt->mysql_template + i;