Able to post Invoice for Blocked stock from quality

Hi

I did GR for material against PO for 50 pcs, During QA32 stock posting i posted 30 pcs to Unres. stock(101) and 20 pieces to blocked stock(350) storage locations.

Now when I am trying to create MIRO invoice verification, I am getting all the 50 pcs and available to post also for the entire quantity. How the system is allowing me to carryout Invoice verification for the blocked stock 20 pcs also ???

It should allow me to process the 30 pcs only which are in unres. stock .

How do I block the blocked stock from getting invoiced ?

Please help

Thanks

Samuel