APERTURE attribute does not work

I test the following element without surface physics (as reported on the OPAL manual: 18.5 Example of an Input File):

FX5: SLIT, L=0.09, ELEMEDGE=0.01,APERTURE={0.005,0.003};

This command is not recognized by OPAL and the slit has no aperture:

OPAL[3]> * Slit x= 0 Slit y= 0 start= 0.01 fn= 
Ippl[3]> FX5 gone live

Btw this information is displayed only with --info 3.

I could reproduce the same effect with different OPAL versions:

OPAL1.4.0 released version: the beam is lost without any error or warning messages

OPAL > 
OPAL > * ************** B U N C H ********************************************************* 
OPAL > * NP              =   10000
OPAL > * Qtot            =    1.60000e-06 [nC]       Qi    =  1.60000e-10 [nC]
....
OPAL > * spos            =    9.14511e-03 [m]
OPAL > * ********************************************************************************** 
OPAL > 
OPAL > 
OPAL > * ************** B U N C H ********************************************************* 
OPAL > * NP              =   1
OPAL > * Qtot            =    1.60000e-10 [nC]       Qi    =  1.60000e-10 [nC]
....
OPAL > * spos            =    1.00250e-01 [m]
OPAL > * ********************************************************************************** 
OPAL > 
Ippl> Save FX5.h5
OPAL> done executing ParallelTTracker at 10:43:43

OPAL/1.5.1-20170217: the beam is lost but at least there is an error message

ParallelTTracker > * Deleted 10000 particles, remaining 0 particles
Warning> reduce: there was nothing to reduce, since the masks were all false.
Warning> reduce: there was nothing to reduce, since the masks were all false.
Warning> reduce: there was nothing to reduce, since the masks were all false.
Warning> reduce: there was nothing to reduce, since the masks were all false.
Warning> reduce: there was nothing to reduce, since the masks were all false.

Solution and Request

1- Don't fix it: in this case the APERTURE has to be removed as element attribute and delete every reference from the manual

2- Fix it: would be the nicer solution since it should allow to create asymmetric apertures in collimators and slits, otherwise not possible