Syntax error

After upgrade iam getting the following error for below code please guide

In Unicode, DESCRIBE LENGTH can only be used with the IN BYTE MODE or

IN CHARACTER MODE addition. is the error message

this part of code

DATA:

L_LMESS LIKE LMESS,

L_LENGTH TYPE I.

DESCRIBE FIELD L_MSGTX LENGTH L_LENGTH.

IF L_LENGTH LT C_MIN_MSGTX_LENGTH.

MESSAGE I000(ZS)

WITH 'The message text variable that you pass to routine'

'GET_BDC_MESSAGE must have a defined length greater'

'than or equal to'

C_MIN_MSGTX_LENGTH.

EXIT.

ENDIF.