UCASE/LCASE only accepts data type "CHAR"

[SUPREMACY17]

While the CAIE pseudocode guide says:

LCASE ()
Returns the string/character with all characters in lower case. The identifier should be of data type string or char.
UCASE ( < identifier>)
Returns the string/character with all characters in upper case. The identifier should be of data type string or char.

The compiler gives the following error:

Runtime Error in file /home/IDE/Buffer/aBmuwycHZqk8Q8LvCgLn9A.pseudo:
Invalid args: expected (Char), got (String)

Traceback:
Program, line 1, column 8

when trying to execute

OUTPUT UCASE("ABD")

Screenshot: