Insert (or update) to a partitioned table returns 0 rows updated

When I insert to (or update) the master table of
partitioned tables, the method's returning 0 (which
indicates that 0 rows are updated). I then checked the
DB and verified that it actually did successfully
insert one entry. My guess for this behavior is that
it's because the updated table is the child table and
not the master table.  Is that expected?

Thanks,
Vince