Reluctantly, I must identify this bug with a CLOSED/WONTFIX one already known for RHEL7. Correcting this limitation in rhel7 systemtap appears to require a rebase from an more recent releases. Rebases require a large burden of proof-of-necessity for this stage of RHEL7.
As an alternative, please wait for the forthcoming DTS9 builds of systemtap for rhel7, which should also contain this fix.
*** This bug has been marked as a duplicate of bug 1332730 ***