ORA-01858: a non-numeric character was found where a numeric was expected TRUNC(SYSDATE)+hour/24

Question

I have a query which runs in sql developer as follows.

UPDATE TEST_tbl SET FAIL_DT=TRUNC(SYSDATE)+08/24,UPDT_DT=SYSDATE, TXT='failed' WHERE SRC='srctest'

when I try to implement the same query in jdbcTemplate with parameter I get the following exception,

ORA-01858: a non-numeric character was found where a numeric was expected

jdbcTemplate.update("UPDATE TEST_tbl SET FAIL_DT=TRUNC(SYSDATE)+?/24, TXT=? WHERE SRC=?",hour,message,srcTable)

where the value of hour can be anything between 0-24.