APEX

Hi,
We run Oracle Retail. We have added an APEX application to allow users to either change their password or receive an email of their password if they "forget" it.
This all works fine.
Looking to refine it my handling non-conforming password changes in the application rather than let the Oracle Database profile return an oracle error to the screen.
So I have my setup like this....
ALTER PROFILE rms_profile PASSWORD_VERIFY_FUNCTION password_verify;
The function works and prevents passwords of less than 6 characters, containing no digits, etc etc etc.
I now want to include this function as a validation in my APEX app. I have the validation defined as a "Function Returning Boolean", containing "RETURN password_verify(:p1_username,:p1_password,:p1_old_password);".
(password_verify has execute granted to public and a public synonym defined - prefixing call with "sys." has same effect).
Whenever the validations are run, for this validation I get {Error ERR-1021 Unable to run "function body returning boolean" validation}.
I have tried using a wrapper package function to call the password_verify function, same problem. If I comment out the password_verify call in the wrapping function the validation executes.
Is there some restriction in calling a profile-linked password verification function from APEX? I can call it successfully in SQL*Plus from the parsing schema.
I can replicate the code in a non-linked function as a work-around, but that would mean whenever we change out password management strategy, I would need to modify two separate functions.
Any pointers appreciated.
Thanks, Rob