Compartment amounts, A(n), used as right hand side quantities in $PK

Dear NMusers, I am doing a simulation in NONMEM 7.2.0. I have an amount compartment A(2) on the right-hand side bioavailability F2 in $PK. I got an error messages as “… 555 WITH A(I), $OMEGA FOR ETAS IN $PK (OR $MSFI NPOP=N) MUST PRECEDE $PK”. In the control file, $OMEGA actually precede $PK. The thing is that the same simulation worked in NONMEM 6. It seems that the feature that “Compartment amounts, A(n), can be used as right hand side quantities in $PK……” has been implemented since NONMEM 6, see slide 16 in http://www.cognigencorp.com/ecpag_org/2006/1_TomLudden_NONMEM_VI.pdf I wonder what could cause this error in NONMEM 7.2, but not in NONMEM 6 and how I can solve this in version 7.2. Thanks for considering help! Xiaoyu