Why does this query return no rows?

[René Fournier]

This query works as expected:

mysql> SELECT id, AsText(coordinates) FROM qs WHERE latitude > 48.6 AND latitude
> < 53.4 AND longitude > -116.4 AND longitude < -111.6 LIMIT 3;
+--------+----------------------------------+
| id     | AsText(coordinates)              |
+--------+----------------------------------+
| 168155 | POINT(48.99702035 -111.60886893) | 
| 168154 | POINT(48.99707385 -111.61983703) | 
| 168160 | POINT(48.99712759 -111.63108001) | 
+--------+----------------------------------+
3 rows in set (0.00 sec)

But this one doesn't:

mysql> SELECT id, AsText(coordinates) FROM qs WHERE
> MBRContains(GeomFromText('POLYGON((48.6 -116.4,53.4 -116.4,53.4 -111.6,48.6 -111.6,48.6
> -116.4))'), coordinates) LIMIT 3;
Empty set (0.00 sec)

What am I doing wrong?

...Rene