Comparing Time extracted from a Datetime column with a Static time in MariaDB and MySQL

Comparing Time extracted from a Datetime column with a Static time in
MariaDB and MySQL

I have a database with a bunch of messages sent between a set of people
and each message has a timestamp in a date-time format. I'm extracting the
time from this date-time column and attempting to compare it with a static
timestamp to see how many messages were sent after that time by each user.
The code I'm using for that is as follows:
SELECT sender_id, SUM(CASE WHEN
DATE_FORMAT(created_at,'%H:%i:%s')>CAST('17:00:00' AS time) THEN 1 ELSE 0
END) AS no_msgs_afterhours GROUP BY sender_id;
The funny thing is this works perfectly in the MariaDB database instance
but in the MySQL instance it gives me this error:
ERROR 1267 (HY000): Illegal mix of collations (utf8_general_ci,COERCIBLE)
and (latin1_swedish_ci,NUMERIC) for operation '>'
The MariaDB instance is version 5.5.32 and the MySQL instance is 5.5.29.
Could this be a MySQL version issue? I read online that there used to be
similar collation issues with MySQL 4.1.8 and earlier but that shouldn't
apply here.