"The urgent amendment to the retrospective provisions of the Act is essential for the wellbeing and safety of children, and their whānau.
"The longer these offenders are off the register, the less ability police have to monitor them."
The amendment will also ensure that any individuals sentenced for a qualifying offence after the Supreme Court decision can be placed on the register, either by confirming their eligibility or enabling review of any decision not to register.
It will also ensure police can register individuals convicted of historical child sex abuse.
Save the Children, a charity that aims to create a better future for kids, welcomed the change.
"Our tamariki deserve the very best protection and for serious sex offenders to be excluded from the registry due to a loophole puts children at unacceptable risk," the charity's Child rights advocacy and research director Jacqui Southey said.
"Today's changes will ensure greater accuracy and transparency on the Register and enable more effective monitoring but we remain concerned that too many children in Aotearoa continue to be harmed by sexual violence.
"We support legislation, policies, and practices that will have greater effect in safeguarding our children."