ORA-00907 when trying to create a CHECK constraint

Question

I am trying to create a check contraint on a table by executing the following SQL statement:

alter table "ApplicationConfiguration" add
constraint APPLICATIONCONFIGURATION_CK1
CHECK (ValueType IN ('string', 'int', 'decimal, 'date', 'time', 'datetime', 'binary'))

but I get the following error:

ORA-00907: Missing right parenthesis

I am completely lost. What am I doing wrong?

Additional information:

• The ApplicationConfiguration table exists and has a column of type nvarchar(32) not null named ValueType
• Database is Oracle 10g Express Release 10.2.0.1.0
• I am executing the statement by using the web client (Application Express 2.1.0.00.39)
• The database user has DBA rights

Thank you!