---
fixes:
  - |
    Fixes performance issue with how the ``basis_gates`` configuration
    attribute was set. Previously there were unintended side-effects to the
    backend class which could cause repeated simulation runtime to
    incrementally increase. Refer to
    `#1229 <https://github.com/Qiskit/qiskit-aer/issues/1229>` for more
    information and examples.
