Tex. Gov't Code § 824.502

The designated beneficiary of a disability retiree who retires before September 1, 1992, who has not selected an optional annuity under Section 824.308, and who dies while receiving a retirement benefit may elect to receive, instead of survivor benefits provided by Section 824.501, a benefit available under Section 824.402, computed as if the decedent had been in service at the time of death.