diff --git a/mysql-test/r/default.result b/mysql-test/r/default.result
index aef49af6c62..e2aa3b4a3cc 100644
--- a/mysql-test/r/default.result
+++ b/mysql-test/r/default.result
@@ -104,3 +104,95 @@ a	b	c	d	e	f	g	h	i	j	k	l	m	n	o	p	q	r	s	t	u	v	w	x	y	z	a1	b1
  	1	0000	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	 	 	NULL	 	 	 	 	NULL	 	 	 	NULL
 drop table t1;
 drop table t2;
+create table bug20691 (i int, d datetime NOT NULL, dn datetime not null default '0000-00-00 00:00:00');
+insert into bug20691 values (1, DEFAULT, DEFAULT), (1, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (1, DEFAULT, DEFAULT);
+Warnings:
+Warning	1364	Field 'd' doesn't have a default value
+Warning	1364	Field 'd' doesn't have a default value
+insert into bug20691 (i) values (2);
+Warnings:
+Warning	1364	Field 'd' doesn't have a default value
+desc bug20691;
+Field	Type	Null	Key	Default	Extra
+i	int(11)	YES		NULL	
+d	datetime	NO			
+dn	datetime	NO		0000-00-00 00:00:00	
+insert into bug20691 values (3, DEFAULT, DEFAULT), (3, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (3, DEFAULT, DEFAULT);
+Warnings:
+Warning	1364	Field 'd' doesn't have a default value
+Warning	1364	Field 'd' doesn't have a default value
+insert into bug20691 (i) values (4);
+Warnings:
+Warning	1364	Field 'd' doesn't have a default value
+insert into bug20691 values (5, DEFAULT, DEFAULT), (5, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (5, DEFAULT, DEFAULT);
+Warnings:
+Warning	1364	Field 'd' doesn't have a default value
+Warning	1364	Field 'd' doesn't have a default value
+SET sql_mode = 'ALLOW_INVALID_DATES';
+insert into bug20691 values (6, DEFAULT, DEFAULT), (6, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (6, DEFAULT, DEFAULT);
+Warnings:
+Warning	1364	Field 'd' doesn't have a default value
+Warning	1364	Field 'd' doesn't have a default value
+SET sql_mode = 'STRICT_ALL_TABLES';
+insert into bug20691 values (7, DEFAULT, DEFAULT), (7, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (7, DEFAULT, DEFAULT);
+ERROR HY000: Field 'd' doesn't have a default value
+select * from bug20691 order by i asc;
+i	d	dn
+1	0000-00-00 00:00:00	0000-00-00 00:00:00
+1	1975-07-10 07:10:03	1978-01-13 14:08:51
+1	0000-00-00 00:00:00	0000-00-00 00:00:00
+2	0000-00-00 00:00:00	0000-00-00 00:00:00
+3	0000-00-00 00:00:00	0000-00-00 00:00:00
+3	1975-07-10 07:10:03	1978-01-13 14:08:51
+3	0000-00-00 00:00:00	0000-00-00 00:00:00
+4	0000-00-00 00:00:00	0000-00-00 00:00:00
+5	0000-00-00 00:00:00	0000-00-00 00:00:00
+5	1975-07-10 07:10:03	1978-01-13 14:08:51
+5	0000-00-00 00:00:00	0000-00-00 00:00:00
+6	0000-00-00 00:00:00	0000-00-00 00:00:00
+6	1975-07-10 07:10:03	1978-01-13 14:08:51
+6	0000-00-00 00:00:00	0000-00-00 00:00:00
+drop table bug20691;
+SET sql_mode = '';
+create table bug20691 (
+a set('one', 'two', 'three') not null,
+b enum('small', 'medium', 'large', 'enormous', 'ellisonego') not null,
+c time not null,
+d date not null,
+e int not null,
+f long not null,
+g blob not null,
+h datetime not null,
+i decimal not null,
+x int);
+insert into bug20691 values (2, 3, 5, '0007-01-01', 11, 13, 17, '0019-01-01 00:00:00', 23, 1);
+insert into bug20691 (x) values (2);
+Warnings:
+Warning	1364	Field 'a' doesn't have a default value
+Warning	1364	Field 'c' doesn't have a default value
+Warning	1364	Field 'd' doesn't have a default value
+Warning	1364	Field 'e' doesn't have a default value
+Warning	1364	Field 'f' doesn't have a default value
+Warning	1364	Field 'g' doesn't have a default value
+Warning	1364	Field 'h' doesn't have a default value
+Warning	1364	Field 'i' doesn't have a default value
+insert into bug20691 values (2, 3, 5, '0007-01-01', 11, 13, 17, '0019-01-01 00:00:00', 23, 3);
+insert into bug20691 values (DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, 4);
+Warnings:
+Warning	1364	Field 'a' doesn't have a default value
+Warning	1364	Field 'b' doesn't have a default value
+Warning	1364	Field 'c' doesn't have a default value
+Warning	1364	Field 'd' doesn't have a default value
+Warning	1364	Field 'e' doesn't have a default value
+Warning	1364	Field 'f' doesn't have a default value
+Warning	1364	Field 'g' doesn't have a default value
+Warning	1364	Field 'h' doesn't have a default value
+Warning	1364	Field 'i' doesn't have a default value
+select * from bug20691 order by x asc;
+a	b	c	d	e	f	g	h	i	x
+two	large	00:00:05	0007-01-01	11	13	17	0019-01-01 00:00:00	23	1
+	small	00:00:00	0000-00-00	0			0000-00-00 00:00:00	0	2
+two	large	00:00:05	0007-01-01	11	13	17	0019-01-01 00:00:00	23	3
+	small	00:00:00	0000-00-00	0			0000-00-00 00:00:00	0	4
+drop table bug20691;
+End of 5.0 tests.
diff --git a/mysql-test/t/default.test b/mysql-test/t/default.test
index b5522394d2d..225ddbc3ee2 100644
--- a/mysql-test/t/default.test
+++ b/mysql-test/t/default.test
@@ -82,3 +82,61 @@ SELECT * from t2;
 drop table t1;
 drop table t2;
 
+
+#
+# Bug#20691: DATETIME col (NOT NULL, NO DEFAULT) may insert garbage when specifying DEFAULT
+#
+# From the docs:
+#  If the column can take NULL as a value, the column is defined with an
+#  explicit DEFAULT NULL clause. This is the same as before 5.0.2.
+#
+#  If the column cannot take NULL as the value, MySQL defines the column with
+#  no explicit DEFAULT clause. For data entry, if an INSERT or REPLACE
+#  statement includes no value for the column, MySQL handles the column
+#  according to the SQL mode in effect at the time:
+#
+#    * If strict SQL mode is not enabled, MySQL sets the column to the
+#      implicit default value for the column data type.
+#
+#    * If strict mode is enabled, an error occurs for transactional tables and
+#      the statement is rolled back. For non-transactional tables, an error
+#      occurs, but if this happens for the second or subsequent row of a
+#      multiple-row statement, the preceding rows will have been inserted.
+#
+create table bug20691 (i int, d datetime NOT NULL, dn datetime not null default '0000-00-00 00:00:00');
+insert into bug20691 values (1, DEFAULT, DEFAULT), (1, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (1, DEFAULT, DEFAULT);
+insert into bug20691 (i) values (2);
+desc bug20691;
+insert into bug20691 values (3, DEFAULT, DEFAULT), (3, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (3, DEFAULT, DEFAULT);
+insert into bug20691 (i) values (4);
+insert into bug20691 values (5, DEFAULT, DEFAULT), (5, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (5, DEFAULT, DEFAULT);
+SET sql_mode = 'ALLOW_INVALID_DATES';
+insert into bug20691 values (6, DEFAULT, DEFAULT), (6, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (6, DEFAULT, DEFAULT);
+SET sql_mode = 'STRICT_ALL_TABLES';
+--error 1364
+insert into bug20691 values (7, DEFAULT, DEFAULT), (7, '1975-07-10 07:10:03', '1978-01-13 14:08:51'), (7, DEFAULT, DEFAULT);
+select * from bug20691 order by i asc;
+drop table bug20691;
+
+SET sql_mode = '';
+create table bug20691 (
+  a set('one', 'two', 'three') not null,
+  b enum('small', 'medium', 'large', 'enormous', 'ellisonego') not null,
+  c time not null,
+  d date not null,
+  e int not null,
+  f long not null,
+  g blob not null,
+  h datetime not null,
+  i decimal not null,
+  x int);
+insert into bug20691 values (2, 3, 5, '0007-01-01', 11, 13, 17, '0019-01-01 00:00:00', 23, 1);
+insert into bug20691 (x) values (2);
+insert into bug20691 values (2, 3, 5, '0007-01-01', 11, 13, 17, '0019-01-01 00:00:00', 23, 3);
+insert into bug20691 values (DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, DEFAULT, 4);
+select * from bug20691 order by x asc;
+drop table bug20691;
+
+###
+--echo End of 5.0 tests.
+
diff --git a/sql/item.cc b/sql/item.cc
index d56ca95093b..d181edb4ecd 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -5379,6 +5379,7 @@ int Item_default_value::save_in_field(Field *field_arg, bool no_conversions)
                             ER(ER_NO_DEFAULT_FOR_FIELD),
                             field_arg->field_name);
       }
+      field_arg->set_default();
       return 1;
     }
     field_arg->set_default();