Using stored function in a SELECT

I'm trying to use a stored function from a SELECT statement, a new feature in 7.1.3, am getting the following error:

ERROR at line 1:
ORA-06571: Function VAL_PER_SINGLE does not guarantee not to update database

Which is described as:

06571, 00000, "Function %s does not guarantee not to update database"
// *Cause: A plsql function that does not have a pragma asserting that it

//          does not write any database state is referenced in a sql statement.
//          Such functions cannot be used in sql statements.

Now the question is, what is the syntax of the pragma to let the db know this function is 'safe' ?

I've looked through all the manuals I can get a hold of and can find no reference to this new pragma.

Thanks in advance.

Grant Johnson                                 Internet: grantj_at_llnl.gov
Lawrence Livermore National Lab	           PacBell Net: (510) 423-0406